As Trump keeps alleging fraud in the 2020 elections, I'm wondering if he has ever explained how he won the 2016 elections in spite of alleged fraud. He said then too that the elections were rigged, but he won anyway, and I'm unaware of any evidence that the 2016 elections actually were rigged (at least, if they were, the fraudsters were terrible since they failed by a quite substantial margin).
Trump proclaimed that he had won both the majority of the popular vote and the majority of the electoral college electors in 2016. The official 2016 results show that he won one but not the other, which got him into the Presidency but which did not provide the moral validation that he wanted.
Don't think of it as one person altering the final outcome, it was many things in many polling localtions which, according to Trump, tilted things against him. But not enough to deny him the Electoral College.
See this tweet.
I wasn't able to find something would resemble a clear explanation he might have offered, but it's worth remembering a few more things about what Trump said about the 2016 and even the 2020 election as well, which might be construed as an implicit narrative.
As o.m. pointed out in their answer (and I did in a comment), soon after the 2016 election Trump declared he also won the popular vote and that the result reported of him losing that popular vote (which has no legal implications anyway) was due to illegal votes...
"In addition to winning the Electoral College in a landslide, I won the popular vote if you deduct the millions of people who voted illegally," said Trump.
In a conversation with Republican lawmakers for which no official minutes were apparently kept, he reportedly put a more precise figure that 3 to 5 million illegal votes had been cast in 2016, and furthermore he insisted in a TV interview that all those votes went to Hilary Clinton. He even gave a scenario how such illegal votes might have been cast:
“You have people registered in two states,” Trump said. “They're registered in a New York and a New Jersey. They vote twice.”
Then he also claimed via his spokesman that there was probably massive fraud in California as well:
His spokesman Sean Spicer identified California as one of the “bigger states” that merit a federal probe into election fraud
In this context, it's also worth remembering the run up to the 2016 election Trump claimed he'd win in NY and CA etc.
“I think we will win New York,” he said in Indiana in April 2016. “I really do.” [...]
His boldest claim in 2016?
“I think we can win the state of California and win it pretty substantially,” he said during a rally in San Jose that June. “Now, I’ve been told by all these geniuses, all these brilliant guys — they all say you can’t win the state of California. I think we can.”
In May 2017 he established by executive order a Presidential Advisory Commission on Election Integrity described a good part of the press as a partisan effort to prove his point that there had been massive fraud favoring Clinton in the 2016 election. The commission was packed with Trump loyalists, some of whom, like its vice chair Kris Kobach had made full-throated statements in support of Trump's claims.
Perhaps pre-echoing the 2020 election lawsuits, the efforts of the Kobach commission were mired in lawsuits and largely failed to turn up evidence in support of Trump's claim. (I won't go over the full history of that here.) Eventually, Trump dismissed his commission in early 2018, without it having issued any written findings and passed the buck on to the DHS. Related to that, in June 2018, a Kobach-led effort to prove fraud (in support of a Kansas law) was dismissed in a federal court of appeal.
For Kobach, the trial should’ve been a moment of glory. He’s been arguing for a decade that voter fraud is a national calamity. Much of his career has been built on this issue, along with his fervent opposition to illegal immigration. (His claim is that unlawful immigrants are precisely the ones voting illegally.) Kobach, who also co-chaired the Trump administration’s short-lived commission on voter fraud, is perhaps the individual most identified with the cause of sniffing out and eradicating phony voter registration.
But things didn’t go well for him in the Kansas City courtroom, as Robinson’s opinion made clear. Kobach’s strongest evidence of non-citizen registration was anemic at best: Over a 20-year period, fewer than 40 non-citizens had attempted to register in one Kansas county that had 130,000 voters. Most of those 40 improper registrations were the result of mistakes or confusion rather than intentional attempts to mislead, and only five of the 40 managed to cast a vote.
As the judge’s opinion noted, Kobach insisted the meager instances of cheating revealed at trial are just “the tip of the iceberg.” As she explained, “This trial was his opportunity to produce credible evidence of that iceberg, but he failed to do so.” Dismissing the testimony by Kobach’s witnesses as unpersuasive, Robinson drew what she called “the more obvious conclusion that there is no iceberg; only an icicle largely created by confusion and administrative error.”
Although Trump had dismissed his commission and courtroom efforts to prove substantial fraud floundered, Kolbach insisted in political statements that e.g. in August 2018
Kobach said there have been more than 1,000 convictions for voter fraud since 2000, and that the commission presented 8,400 instances of double voting in the 2016 election in 20 states.
“Had the commission done the same analysis of all 50 states, the number would have been exponentially higher,” Kobach said.
In response, Dunlap [a minority Democrat on the commission] said those figures were never brought before the commission, and that Kobach hasn’t presented any evidence for his claims of double voting.
“The plural of anecdote is not data,” Dunlap said in his Friday letter to the shuttered commission’s leaders.
My point with all this is that while Trump may not have given an explanation exactly to the the OP's question, throughout his presidency, he and his supporters have continued to push a narrative that voter fraud was favoring Democrats, if simply by the implied logic that such Democratic strongholds ought to have voted Republican had it not been for the "double voting" and/or illegal immigrants voting against Trump, legal setbacks proving such phenomena were widespread notwithstanding. (Through legal meanders that are not entirely clear to me, the Kanasas law was struck down (on appeal) in the summer 2020, by the 10th Circuit, although it might be ultimately headed to the Supreme Court.)