My guess would be there was probably some rule violation that occurred at some point during the TB that made them decide to kick you, but since members can't participate in TB if they join midway through it a lot of guilds wait until after TB has ended to kick people who don't live up to guild expectations in some form or another so that they don't sell themselves short by parting ways.
That being said, guilds will usually still let people collect their rewards before kicking them unless they have committed a very grave offense or maybe even one they've been warned about multiple times.
But there are some mean or elitist guilds who don't care at all about those who don't live up to their standards.
Not sure which scenario is better for you. Sorry about your luck.