This isn't a simple question, but I just wanted to mention that around the turn of the 20th century, there were a lot of changes in math. A bunch of fields got

This isn't a simple question, but I just wanted to mention that around the turn of the 20th century, there were a lot of changes in math. A bunch of fields got reformulated and there was a rush of mathematicians coming up with new ways to express problems, which led to brand new fields. These ideas then filter into other sciences, allowing for those researchers to better describe and solve problems, etc. That isn't to say this is the only reason, but it's a contributing factor.