First, fairness != resentment. One is a quantifiable statement, and the other is a feeling. It would not be fair to me if I didn't get the stimulus while everyone else did, but I would still be quite happy for everyone else.
> Now think about it in terms of income inequality. If someone makes $1M per year, why do you care? It doesn't hurt you.
I don't care, because by itself, someone else earning $1M per year doesn't affect me.
What I do care about is when people turn their wealth into power, because that does affect me (and many others). Like, income inequality wouldn't be a problem if the high-income people didn't keep using their wealth to exert undue influence (to put it politely) in politics, religion, media, and other shared aspects of our society.
See the difference? I don't resent people for being wealthy. My feelings towards them depend on the things they do with it.