Just because you own a company doesn’t mean you are a good leader, he has shown no leadership qualities, he seems to 2nd guess himself a lot and make really poor decisions. Example morally yeah it was the right thing to do helping Norah Dahrk, but he got himself captured. That’s the kind of decision that is why he isn’t the leader. Sarah and Amaya have shown they can make the sacrifices and the hard decisions. Would have realised they’ve just won the battle and taken that.
There was an episode where basically this played out with Stein wanting to be Captain, he teaches is supposedly a brilliant professor but he can’t make the snap decisions, hard decsiscions and panics. Sarah can and Amaya has also shown this to be the case.
I’m also pretty sure that Sarah put Jax in charge over the others before and I’m sure on 1 occasion she puts Mick in charge over Rey.