Posting as one or two works

I'm rewriting something I wrote in 2020 and it's two parts (maybe three, depends of how it ends). When I posted the first version, I noticed the drop in engagement in the sequel. I don't know if it was the actual story or the fact that it was a different work.

I've seen fics that are a series but all in one work, they get extremely long but that's no the point.

Should I post it in one or two works?

I'm not even sure I'll finish it and post, but I'm considering the posting already.