Even during youth leagues, he always had his own training techniques. He's stubbornly stuck to them against the advice of every trainer and coach he's had in his life. When he started having some success in the majors, other pitchers started to emulate him, it wouldn't surprise me if people started looking more closely at his techniques and started to adopt them.
On the other hand, his career was circling the drain, then he started to cheat full steam ahead with the sticky stuff, and won the Cy Young that season. Overall, his career isn't uncommon for a player to have some good years, then start to lose it and fade away. Some players decide to start cheating to keep it going longer, Bauer is one of those.