Your general point is well-made: we often expect others to behave rationally while we utterly fail to behave rationally ourselves. Voting for Trump or for Brexit are obvious examples of people doing astoundingly stupid things entirely against their own self-interest, merely because they believe some mindless babble. Putin is not any more intelligent than the average human being but, being totally isolated and living in a toxic fantasy world, has acquired beliefs that are in no way mapping to reality. Not surprisingly, the results are catastrophic. This is the problem all dictators face, and is why they always without exception destroy their own nations in the end.