It's hard to believe that they all would betray their Shinigami. Some of them had really good relationships, or at least I thought so

i have no idea you never know

Everybody wants to gasp little freedom... They went out to play a little, train their captains to grow stronger and more important once again to see if they are worthy of having them as their zanpaktou... So they made free choise on this just because of that. But you've seen how Senbonzakura Kageyoshi is plain little weird, it must be that something happened with fighting Byakuya, maybe his zanpaktou is having doubts in this rebellion now...

there is something up because a zanpakuto is one with its user also if you didnt notice Zangestu seemed not at all to want to betray ichigo till muramasa meet him

ps lol sorry about unjoining fate night i was going throw and deleteing spots i didnt me to shwele i will re-add it right now you can even check if youd like

Muramasa keeps pulling them back, too. It seemed that after Rukia fought and "freed" her zanpakuto, Sode no Shirayuki started to go after her and apologize or whatever, and Muramasa showed up and stopped her.