Here's why: https://www.youtube.com/watch?v=S2pr1AyTrIQ
Muddy the Tories are a tribal party. They backed Boris as PM so they're prepared to swallow this Brexit sell out. Look at Rees-Mogg - who I like - saying we'd be a vassal state under Mrs May's deal then on the third time of asking he voted for it. The Tories have no principles except one, compromise. But as stated earlier a compromise on Brexit is Remain.
We're going to see over the coming month who argues the most consistently. Who presents the detail in Boris' deal in the most convincing way. I don't think it will be Boris because as demonstrated in parliament he hasn't grasped the details.