This question is primarily opinion-based to some extent so I've tried to quote as many sources as possible. Any feedback is welcomed in comments.
It's mainly because it's more complicated and some believed that Russia's actions would undermine the US election and US democracy.
As quoted from the Intelligence Community Assessment report:
Russia’s goals were to undermine public faith in the US democratic process, denigrate Secretary Clinton, and harm her electability and potential presidency. We further assess Putin and the Russian Government developed a clear preference for President-elect Trump. We have high confidence in these judgments.
As quoted from this article by Quartz:
How big a threat is Russia, really?
It’s a serious threat. Putin seeks to weaken the US, the EU, and NATO to the degree that they can no longer presume to call the shots without his agreement in international affairs. Since western governments are not ordinarily prepared for such stout challenges to their democracies, they are vulnerable to the weapons of doubt he is employing, mainly creating the impression that there are no indisputable facts, that anything could be true, and that everything is either already compromised, or could be. Since trust is the bedrock of democracy, this threatens social stability across the West.
Also, if the Russians are successful this time, they would try to interfere in future elections in the West, such as the French presidential election this year. In this way, they would try to elect leaders who are "more friendly" towards them and develop stronger bilateral ties which would benefit them and put them on the world stage.
You can check out this article for some of the comments made by Republicans lawmakers on the reasons why they're "so obsessed" with the investigation.
Russians officials would obviously deny the claim. Since the Russian government hope to reset ties with the Trump administration, publicly acknowledging that they did it would put Trump in a difficult position should he want to rebuild ties with Russia. Furthermore, the Obama administration had already imposed sanctions on Russia after the election. By publicly acknowledging the claim, it would mean the sanctions would be justified.
The few instances you listed doesn't really interfere with the election since they're just stating their opinions.
For example, if John tells someone that he doesn't support Trump compared to Tom hacking a presidential candidate's emails and releasing potentially confidential and private emails that would reveal discussions within the campaign. This would give the public information that they aren't supposed to know.
One such example is that the DNC had favored Hillary over Bernie to be the Democratic Presidential Nominee. If the emails aren't released, the public wouldn't know that. Similarly, if someone hacked Trump's tax returns and released them, it would also be illegal.
So, the examples you listed basically aren't similar with the scale of the Russian interference at all.