>Populism creates problems or do not solve them in order to exist.

Why is this unique to Populism? Most forms of power or organizations in general rely on there being a problem to solve.

You are probably right, my point is that Populism, and at least it, does need to perpetuate de problems, hence, no populist leader is/was ever effective.

Not an answer but an appendix. There is common misconceptions on the definition of politics. For the masses politics means to define policies through negotiation and prioritisation. For politicians, it means something related to exert political power.

I agree with the point that populists have a strong incentive to not solve problems, but I'm not sure that means populists can't be effective. For example in US history FDR was arguably a populist, and I would say pretty effective. And while the US populist party imploded fairly quickly, a good chunk of it's policy wants wound up happening in the next decade or two during the progressive movement.[1]

Using the power definition of politics, it still seems to me that because the ability to exert power is only given when there is a need to be solved, a (for example) plutocrat has a similar incentive not to solve problems as a populist, and would be similarly likely to not be effective. I suppose an explanation that's consistent with both perspectives is that political leaders in general are not effective.

[1] https://historymatters.gmu.edu/d/5361/