If your explanation requires assuming that both very powerful politicians and their supports, constituting tens of millions of people, are all incompetent, then perhaps you need to consider an explanation that doesn't require such assumptions.
I'm not assuming the politicians are incompetent. Usually, they aren't, they're just working towards different goals then their constituents or what they promised them.
If you really think the average voter is competent at economic matters, I have a bridge to sell you...
> 1 In 4 Americans Thinks The Sun Goes Around The Earth, Survey Says
i.e. about as much as voted for each of Trump/Clinton in the last election (which also taught us, amongst other things, that surveys are not to be trusted...)
