Ronnie never dominated 9 ball. When the IPT was starting out he played in some 9 ball tourneys and I believe he had a runner up but that is about it. He did alright in the IPT but he was still an underdog to the top players.
You are right though, there are a lot of similarities. Pattern play, breaking into the clusters, nudging balls are apart of both games. I've taken elements from both games and cross introduced each other.
Ronnie is in my opinion up there with Walter Lindrum as one of the greatest players to ever touch a cue, regardless of discipline. But he would have to dedicate himself to pool in order to dominate. If he entered the World 14.1 Championships this year I think he would make it out of the Round Robin stages, but I don't think he would make it to the round of 16.
As good as the snooker players are, we have to remember pool players are just as good at pool. He would have a rough time with John Schmidt, Danny Harriman or Thorsten Hohmann. Marop recently posted that John Schmidt ran 20 100+ runs (including some 200's) over the course of 5 days, that is ridiculously good.
The games require different skill sets. If I may use myself as an example, I have been focusing almost exclusively on snooker and playing very limited pool. My game has been pretty good recently, I've made a couple of centuries and a couple of 90sumthins within the last few weeks.
By contrast my neglected 9 ball game is in the pits. Where I used to be able to consistently beat the 9 ball ghost, it's now a battle and if I do win it's not by much. Furthermore it's been a while since I had a run over 40 in straight pool.
I believe Ronnie could make it to the top of the pool world, but he would have to dedicate himself to it and it would be at least a couple of years until it all comes together.