So here’s a question: do you really need over 2,000 followers on social media before you bother submitting your manuscript to agents?
Tl;dr, no (I certainly didn’t), but.
The “but” there is that someone with a ready-made established fanbase is an easier sell to editors than a 100% unknown. This is, after all, why celebrities get book deals. So someone with a fat wallet of past success is very likely to get a better deal on the MS sale than someone coming completely out of left field… but that’s about it. Ultimately, agents and editors will pick up good, saleable manuscripts no matter who wrote them.