Wow, crazy games. Unfortunately for you playoff crunch time is the default. It looks like they went bot sometime during season 9 (probably towards the beginning) and were then moved to D.V in a bot sweep.
I'm in a somewhat similar situation, where the team I'm playing in the finals just went bot and they had a monster player. Fortunately for me, he went all free agent on them
(2254577), so now I don't have to face him in the finals.
I can confirm, from several of my leaguemates going bot over the course of the season, that their roster stays intact until a new manager is appointed to take over the team. In my league, this happens fairly quickly, but apparently it doesn't in yours. Does anyone know how they determine which team a new manager should take over? They obviously can't place someone in D.II, and probably not D.III, but my brother was put in D.IV and I am in D.V. Do they just start at IV.1 and fill all the bots until they get to IV.64, and then start over at V.1?