The incredible speed with which Disney fired James Gunn is interesting.
Gunn could've been fired for many reasons. One reason could be that he's much worse than his social media profile alone indicates and Disney wanted to cut him loose immediately before anything else came out. More generally, someone(s) at Disney know more about Gunn than we do and based on what they know they made a quick decision to fire Gunn.
Disney may employ many evil people but they have an image to protect. Disney desperately wants to continue to be thought of as a family friendly brand.