LOST nerd here! I'm not sure where the information about Damon Lindeloff leaving the show came from. As far as I know, he and Carlton Cuse were showrunners all six seasons and had writing credits for episodes in each season. They had a "series Bible" from early on with the overarching story, so I don't think they got lost (hiyooo!) along the way. There definitely were times in seasons 2+3 where they weren't sure if they were going to get renewed, so there was an odd balance of trying to tell the overarching story without knowing how many episodes they had left to do so. I also think the finale is commonly misunderstood, but I'll spare a longer comment about that. ;)