Viewed through an incredibly cynical lens, the wealthy folks supporting Biden know that income inequality is at its highest point, and that many people are (deservedly so) fed up with disgusting displays of wealth. To them, they would much rather eat the cost of a tax increase to keep the proles content, than to risk getting guillotined. I wouldn't put it past them if this move was solely in the interest of self-preservation and maintenance of at least some of their fortunes, rather than true investment and belief in such causes.
How is that cynical? That's precisely what's happening.