Yes, this is mainly the answer. Politicians failing? Well, we had that all the time. When was there a period when politicians did everything right all over the world? From a German point of perspective, after WWII we had the 50s with Nazis returning unscathed to many positions of power, the SPIEGEL affair where government critical news should be censored, then the 60s with the Cuba crisis and the student revolts, the 70s with the terror of the RAF, the 80s with the environmental panic, the 90s with the Neonazi murders in Solingen etc, mass refugees from the former communist states, the 2000s with Al Qaeda terror and the world-wide financial crisis - there have always been problems that seemed like the end of the world in the respective era. And in all cases, politicians could arguably have acted better than they did.
So "failing politicians" can't be the real point to explain what is going on, as it would be necessary to explain why somehow at some point nearly everywhere in the world politicians start to fail.
Also, the situation can be seen in such different countries as the USA, Turkey, the Philippines or Hungary (and many many more), making it difficult to blame a specific culture or way of thinking.
But one thing is common: the access to the internet, with its abundance of unproven sources of information. Whatever your political opinion may be, you will find sources where it is "proven" that this opinion is the ultimate best with no disadvantages. In former years, most of the information that was easily accessable went to a long process of checking (and, arguably, censoring) so that the presented political options remained quite narrow. Some things might have changed over time (for example, the acceptance of homosexuality), but in general, especially concerning fundamental views about democracy, capitalism, liberalism etc., nothing changed much. There was the Soviet Union as the only alternative role model, and it failed miserably. So, political discourse was narrowed down strongly, or at least confined to a relatively slow pace.
Enter internet. This directly bypassed the predominant ways of generating public opinion by enabling practically everyone to announce the own political views - and to realize how many people actually supported these views. The result is a much faster pace of development of political opinions; too fast to be checked and shaped in a moderate way, so those ideas remain edgy and ugly and untested, but require immediate implementation "because democracy".
The best example for this is Donald Trump, the archetype of a populist politician. Most of his decisions are impulsive and sort of ugly (which means that he often just says what is in his mind, rather than making a well-designed argument), they are often inconsistent ("North Korea is evil!" - "Me and Kim will meet soon!" - "I will not meet Kim!" - "Maybe I will still meet Kim!") and confusing. That doesn't mean that they are necessarily all wrong, it is just that the pace of events has quickened up, leaving few room for checking and balanced measures. Populism is the hecticness of the public mind, amplified by the internet and clotted as politics.
And yes, there have been populists at least since the Roman Republic, but the amplification of the Internet has made the things much worse.