Biggest cause for oblique strains is heavy lifting such as weights which is a big norm for athletes these days. add that to all the normal twisting, throwing motions, and bending a baseball player does every day and boom it due to happen more now.
Same with the hamstring issues, Compared to way back in the day when Athletes just mostly stretched, did light lifting, and ran to stay fit, these guys now do some heavy lifting which builds up muscles but increases the chance of strains and pulls if they're not stretched out enough to deal with all the movements they do in games.