The Treaty was always just an excuse, given that Germany started to remilitarize in secret almost immediately. That was expected though, which is why France went through such lengths to surround Germany with, if not hostile powers, then at least non-subservient ones.

What really made it happen was that France, Germany, and the USSR were all run by idiots: France sat around until it was stuck with an unwinnable war, Russia helped Germany get into a position where Russia could very well have been stuck fighting a one-front war against an enemy it had lost to while fighting on two, and Hitler kept lying about his objectives, and was somehow surprised when people assumed he just wanted to conquer the entire world and reacted as such.