alt Hacker NewsVoting "insane" is very different from voting "selfish".
Clearly, voters are not casting votes based on objective measurements of the things that some candidates believe are important to them (e.g. household income, life expectancy, health care quality etc).
But that means either that they are voting based on other issues that they consider important, or they are not voting based on likely outcomes of a candidate's policy preferences at all.
It's not trivial to differentiate these two (and of course, there may even be a mixture of all 2, or even all 3, reasons to vote).
In a republic, where you vote for people to represent you, not to implement your wishes, voting for a candidate you believe will make "good" decisions (even if you disagree with some of them), is actually how the system was supposed to behave. "Good" might mean "the things I want / agree with", but it might also mean "benefits the public interest, even if I don't want / disagree with it".