May has acted throughout like a PM with a huge majority behind her. She has failed to consult with other parties, or even with most of her own, she has failed to give information about the negotiation to parliament. Now this has come back to bite her and the country is in total disarray.
Corbyn has failed to have a clear position on anything, adding to the chaos.
Parliament has taken back control, but too late.
Corbyn was more or less obliged to submit a motion of no confidence, this was a defeat of historic significance, even just by the numbers. The government cannot pass its most important piece of legislation so parliament cannot have confidence in it (although I am sure that the tories will fall back in line tomorrow).