The Fly Ball/Pull Rate paired with the Solid Contact/Barrel Rate
You could tell something was different about the way that Crawford was hitting, and it's reflected when you go and look at his underlying stats. Not blessed with a lot of power, Crawford used to work on hitting the ball up the middle and oppo more often than most. His Pull/Straight/Push rate from 2020-2022 was 32.9/37.8/29.2 (rounding). In 2023, it was 43.2/34.1/27.2. He was only going oppo a little less, but he was turning on the ball a lot more, just over 1 in 10 times he put the ball in play.
That's not always a good indicator, as you will sometimes see it by a player who is trying to only hit homers, usually later in their career. However, JP was pairing this with an increase in both his solid contact and his barrel rate. His barrel rate in that 3 year span was about 2.1% with a 4.6% solid contact rate. Those numbers jumped to 4.8% and 6.6%, respectively, in 2024.
This wasn't a straight home run swing, though. His line drive rate stayed the same, but he just shifted to a lower ground ball rate and a higher fly ball rate. More balls hard hit, and more of them in the air off the barrel. His exit velo jumped from a bottom 5-10% of the league up to bottom 30%, which is still a 2.5-3.0 mph difference, and a big change. That's a full season of increasing all aspects of hitting the ball harder, more consistently hitting it harder, and having it leave the bat at a better angle.