There are plenty of better places for them to do this.
yes there might be safer locations for an underground nuclear test, but how many of them offer the same "F U" PR capacity relative to Mexico/Juarez/cartels, etc.
Nukes mean nothing to a cartel. What an insane idea.
Fantasy often likes extreme options but most probably saner reason like expected strike on cartels and their retaliation is whats happening.
So 100% Trump