First of all, I think we were both wrong when we said “pitchers have always thrown as hard as possible.” We’ve all seen All Star games where pitchers were typically watch throw 93-94mph are suddenly hitting 98-99mph. Could be different radar guns, but it’s also possibly pitchers pacing themselves. Certainly starting pitchers throw fewer IP than they did 15 years ago, and relievers throw more, and the role of the bullpen has expanded in both IP and roster spots.
Shift Ban Supporter Freddie Freeman confirmed that nowadays it’s not so simple to go the other way because “everyone throws 95 mph.” Maybe the reduced IP from starting pitchers throw fewer - an ongoing trend - appears to have encouraged pitchers to throw even harder. Maybe pace themselves less. I could see this causing issues. Maybe.
Honestly looking over that blog data, there likely isn’t a single cause beyond simply pitching. With 390 roster spots dedicated to probably 800-900 pitchers over the course of a season, the range in the number of MLB Tommy John candidates isnt so large, ranging from 1 (2005) to 11 (2014, 2021). And none of them happened to a pitcher who started pitching that year. Ergonomically, every pitcher is different, capable of handling different limits. But over years of repetitive pitching motions, occasionally something will go wrong…