>>212662115This is a myth. Straczynski played fast and loose the whole time.
The actor who played Sinclair developed extreme schizophrenia during the first season. He started having unpredictable outbursts and started alienating the other cast members and crew. He privately confided in Straczynski that he couldn't act anymore, but he didn't want people to know in case he could get treatment and was able to become a working actor again. Having the main character of a show abruptly quit has been a death knell for a lot of shows. So Straczynski wrote a letter to the fans lying about 'Oh, no worries, I totes prepared trap doors, it's normal to write the possibility that every actor will suddenly quit, I am not making this up on the spot'.
Lyta got replaced because the Garibaldi actor wanted to get with the Talia actress. Talia got replaced because her actress was married to the Garibaldi actor and they got divorced, their inability to work together made it impossible to film episodes and Garibaldi was more important to the plot.
Keffer got killed off because a studio note created him, Straczynski was always bitter about that, so he killed him off.
Ivonova was replaced because Straczynski started creeping on her days after her divorce, and she was justifiably like 'no, I don't want to date anyone, gross, also you are my boss', so he had her S5 contract show up at her address at 2AM demanding she sign immediately sight unseen and of course she said 'Uhhhhh... no. That's not how it works, feels like you are doing it this way to contrive a way for me to no longer be on the show.' She refused to sign and he said 321 no backsies.
The letter became an excuse he had to use repeatedly. These are not the actions of a careful chess master, it was always on the fly.