"a_plutonium" schreef
So what is the deal with cambium and what does it take to kill a tree
by its cambium?

***
This rather depends. The cambium layer itself is very thin and easily
destroyed. However the tree has some capability to repair the cambium layer.

Basic rule might be: if it is a tree you want killed, then it will take more
than you think to actually kill the tree. If it is a tree you want to keep
then it will be more easily killed than you would have hoped for.
PvR