If the stats are to be believed:
-In 2008
18 pitchers in the league could throw over 100 mph and through the whole season they combined threw 196 pitches over 100+ mph
-In 2017
40 pitchers in the league could throw over 100 mph and through the whole season combined for 1,017 pitches over 100+ mph.
HGH comes to mind but they're clearly doping and getting away with it. What do you suppose they're using?
I remember when creatine became popular and it was a controversy as players began to shatter home run records left and right. Granted that's just the result of an increase in leverage and isn't related to steroids per say.
I saw a really interesting thing from Gorge St Pierre, a UFC fighter, about how athletes get around drug testing. I'll see if I can find it. The gist of it was there are drugs that are taken which are supposed to be 24 or 48 hour lifetime in the system and athletes plan around beig unavailable at these times for random drug testing ie;they will say they are travelling and just go hide for a day or so.
I think its just more people training for it from an earlier age. When Nolan Ryan started pitching, a 100mph pitch was unheard of. You might as well have been talking about a 4 minute mile.
Are you sure it's not training? Similar things with speed and safety regulations in the NHL. They more or less outlawed hard hits and fighting to keep players from getting seriously hurt--namely concussions. Fighting is almost nonexistent at this point but there's more concussions than ever. Because enforcers aren't needed, everybody is fast--fast is the new strong. They're also getting taller and heavier from training. Well, speed and momentum = big fucking hits.
So, back to baseball. Can't dope anymore, so they train real hard. Now everybody does it. Thus you have a lot of people suddenly able to do these feats.