If any number of economists can hold the same number of views about how to manage an economy, why is it surprising that politicians are no wiser. They believe in one particular system or another because its a shiboleth they hold on to to save them the trouble of understanding it.
(Incidentally and slightly off-topic, but likely to excite a reaction, I was browsing the website of "Pravda" as is occasionally my wont, and I noticed the American political system was described as a one-party police state - implying the Democratic and Republican parties are just two sides of the same base coin ... I'll leave that thought for someone else to pick up ... )