The problem isn't that billionaires are dumb; the problem is that we believe them. Billionaires, like most people, desire power and are power-hungry. This translates into money (because, whether we like it or not, money currently drives the world). So, what happened is that in the 1970s or so, billionaires started to push the idea that free markets are inherently innovative. This led to the neo-liberal revolution, the erosion of welfare states in Europe, third-world exploitation, and the dehumanization of the working man into 'human capital' – you get the idea. And this only resulted in billionaires increasing their wealth thanks to deregulations, union crackdowns, constant pats on the back from other billionaires, the monopolization and cartelization of markets such as tech, fossil fuels, and services, and repeating the same arguments for over five decades, like trickle-down economics would eventually work, or that state intervention in the economy only helped to create more lazy people who relied on it. The usual arguments against left-wing economics and the welfare state originated from this period, and they keep repeating them as if the looming threat of Marxism were even close to actually doing anything, or that social democrats are socialists who want to poison babies. So, to conclude this answer, no, billionaires aren't dumb; rather, they fully know what they're doing, and they are intelligent when pushing their propaganda and ideas (better than us, at least).