Rowling was always known to be slightly racist but people mostly dismissed it as a sort of fantastically stupid racism. As in, the "ha ha this racist stereotype is so dumb, see how ridiculous it looks when I put it in my wizard book" sort.

I don't think it was until she started going full TERF that people began to realise that she's not making fun of the stereotypes; she actually thinks casual racism is a funny and cute thing to do.