Because both parties donate to Istrael, and both parties deny relief to poor Americans. The problem for the democrats is that their base isn't toxic enough to enjoy the deprivation of others for its own sake, while republicans have done away with any facade of being decent and will (mostly truthfully) imagine that the aid is being denied to black people and other non-white people
more broadly the liberal wing is a bunch of rich people who want to pretend to help other people, instead of rich people who want to openly kill people