Because it's popular. Vilification of merchants for being merchants is a tradition at least as old as recorded history. Vilification of the rich for being rich is much less old, but it's a quite robust tradition of the American Democratic party. Vilification of "corporations" for being corporations is even more robust.

>Vilification of the rich for being rich is much less old

The idea of struggle between the lowly commoners and the powerful elites goes back to at least the Roman Republic if not even further.

https://en.wikipedia.org/wiki/Secessio_plebis

Sure, but that's not at all the same as the idea that the wealth of the rich demonstrates that they are evil.