P.T. Barnum famously - and accurately - remarked that no one ever loses money by under-estimating the intelligence of an audience. On the whole, people are not stupid; they are extremely stupid. The average person knows almost nothing and understands even less. The average person crams their head with ephemeral trivia about sports teams and reality TV shows; otherwise their brains are devoid of anything remotely approaching knowledge and as for understanding, well... let's just say the least said about that the better.
Not surprisingly, given a system in which anyone can vote regardless of how ignorant and foolish they are, we get the outcomes we see all around the world. Populism triumphs because that's what ordinary people vote for. And ordinary people are even less able to grasp consequences than tiny children clamoring for endless ice-cream and candies.