I think you're giving people way too much credit.
In what way?
You think they act in their own self-interest.
Not always. I think they -think- they act in their own self interest, but that doesn't mean they always do. This is actually one of the points brought up in regards to low information voters. Quoting from Wikipedia's low information voter article:
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Voting correctly
Related to the concept of a low information voter, voting correctly is a concept from political psychology that refers to a vote decision "that is the same as the choice which would have been made under conditions of full information."[12] Measurements of correct votes are used to determine how accurate low information voters are at determining the candidate or party that best represents the voters' interests.
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Source:
https://en.wikipedia.org/wiki/Low_information_voter#Voting_correctly