FWIW, here is where satellites are distributed:

LEO:84%, MEO:3%, GEO:12% (https://nanoavionics.com/blog/how-many-satellites-are-in-spa...)

Combine that with the increased volume at higher elevations, and you get much higher satellite density in LEO. So if there is any Kessler problem, it will likely happen in LEO first. And that is the place that is the easiest to deal with (or quickest to self-heal by orbit decay).