Here is an informative quote about Carlos Rodon‘s transformation from good pitcher to great pitcher:

It is not quite accurate that Carlos Rodon was a late bloomer; he was a late learner.

…

It was not until 2018 or ’19, he said, when technology such as TrackMan began proliferating around the game that he learned about his arsenal. The more over-the-top he released his fastball, the less hittable it became. In his terrific 2022 with San Francisco, the big lefty, on average, spun his four-seamer from 6 feet, 6 inches away from the ground, far higher than most.

NYPost.com

The article contains an excellent discussion of why Rodon’s stuff works so well. The over the top fastball drops much less than most fastballs. That lack of drop causes batters to swing under the pitch. It’s what made Matt Cain so good.

You can see Rodon’s change in his batted ball data. Notice how in 2020 his Infield Flies as a percentage of fly balls increased. It came down a bit since then, but his still higher than his career average the last two season. He also saw a reduction in home runs per fly ball, as batters still get under the long flies.

The stuff was always there. Technology helped Rodon to use this arsenal more effectively.