Also,

Lae’zel - foot soldier, used to following orders
Shadowheart - acolyte of a religious cult, used to following orders
Astarion - literal slave
Wyll - talks a big game but is clearly a bit full of crap and definitely not leadership material
Gale - has a big ego but doesn’t seem to possess the managerial people skills or the interest in stepping into a leadership role, seems more like a power behind the thrown sort
Karlach - you save her life
Minsc - years of canonical experience following a leader
Jaheira - ditto

I don’t think it’s strange that, given the pressing circumstances, any of these characters would fall in line behind a decisive, authoritative type-A personality.