It's not a CIA op or something. It's just anti-semitism.
Vatican II included a stance of not blaming jews everywhere for the death of christ and opened itself up to the ideas of other religions and science.
This ended up leading to an apology for the persecution of astronomers such as Galileo and Copernicus years later
They use the flat earth thing as a dog whistle for wanting the Catholic Church to go back to its old ways.
That's all it is. It's just trad cath fascists jerking themselves off and some dumb guys following along not realizing what they're doing.
I feel like the youtube video In Search Of A Flat Earth goes into your subject really well. I dont know if you have seen it but check it out if you have not.
Lol yeah this rules said it a million times better than me