People wanted to pit Kate and Meghan against each other and to be fair their fans really bought into it
I don't think Kate's real fans have done that, just those who originally didn't like Kate/were neutral about her. They now love Kate and use her as a shield to criticise Meghan.
You can also see this in tabloid newspaper article comment sections - a few years ago, Kate was constantly described by them as being lazy, girly, superficial, faking illness, boring, flashing, not independent, self promoting, unconfident, etc. Now they love her, Kate can't really do anything wrong and Meghan can't do anything right.
The newspapers see how they receive lots of engagement by bigging up some, whilst putting down others and then run with it. They thrive by doing that.
I was particularly disgusted when they quickly began changing the narrative and deleting/covering up negative past articles on the likes of Diana and Caroline Flack following their deaths.