I think he had to go in favour of Remain for the party, as they are mostly Remainers. He couldn't divide the party like Cameron and Boris did.
Now imagine if the Labour MPs stood by Corbyn, this is what I think the situation would be:
By calling on the Governent to invoke Article 50, he was essentially challenging them. Knowing the PM was a Remainer and not wanting to do it, it put pressure on the rest of the party whilst its in a state of limbo as the party was so split over the referendum.
Given that Corbyn is a Leaver and that he's called for Article 50 to be invoked, I think he may be the only one with some sort of plan.
The question is, does he outline his plan, thus giving it on a platter to the Tories for them to rescue their situation, or does he hold his cards to his chest, put pressure on the government to see it fracture further and then take advantage of the mess to push Labour to the forefront..?
Only now the Labour MPs are revolting and causing a divide amongst the party which rips up any form of plan that they may have had and balances out the problems in both Labour and the Tories instead of pushing Labour to the fore.
The public voted to Leave, so leaving is on the table. If we do, things will get worse before they get better. Corbyn is the only politician I have faith in doing the right thing for the common man during those times!