system
Given the following post, respond as if you're commenting on Reddit:
human
Why does fission happen randomly?

It seems for a given nucleus either the Coulomb repulsion would overcome the strong force, or the vice versa.  From where does probability get involved?
gpt
Spontaneous fission is a quantum tunneling process. You have two (or more) "lobes" of nuclear matter, bound by a mutually attracting potential. In order for fission to occur, they must tunnel out of their attractive wells. Depending on how strongly deformed the nucleus is, this could be very easy (meaning small lifetime) or very hard (long lifetime).

Exactly when tunneling will occur is of course probabilistic.