The last bubble pop was around 2012/2013.
A combination of a shift in the toyline, too many large expensive drops and multiple sister companies mixed with many, MANY customizers releasing figures every day and the 3 dozen or so people scooping up hard to find figures from the first 2 years for $100 a pop all built in this crazy wave of expansion and then a sharp decline that unironically almost killed glyos. Basically people were buying and selling so much of each other's things and new buyers tapered off and old buyers exited with the death of detail lines and having exhausted buying core molds with every color of the rainbow.
Things are not the same as that, but there are certain similar aspects. More sister companies than ever, customs are making a comeback and 3D printed figures have replaced resin with tons and tons of new makers popping up. The key difference here and something that may save it is that Corona paused and greatly slowed down production. Matt has moved to reduced releases which could build up demand and keep things going fine for a while. However if corona hadn't happened and we continued on the breakneck pace of sometimes multiple drops per week from different companies I could easily have seen a bubble pop.