And the founder of Sinn Fein, Arthur Griffiths, was one of the most pro-Treaty men. Funny how the wheel has gone full circle.
DeValera was jealous of Collins. He reckoned the best way to put him down was to send him to the UK to try and negotiate the unnegotiable (i.e. a Republic) and he would then come back a failure. However, when Collins signed the Treaty because he knew this was the best they'd get and the IRA was on its knees, DeValera (who has spent most of the Troubles out of harms way in the USA) couldn't accept it because he'd have to play second fiddle to Collins. Now, there probably would have been a civil war even without Dev but he bears most of the blame and his motives were mostly personal rather than political - although obviously he did believe the terms weren't acceptable.