The Fox News agenda, like any corporation, is to make money. This is the reason they cater to Republican causes because they often have the deepest pockets willing to spend on stupid shit rather than philanthropic endeavors.
They liked Tucker when he was making them lots of money. They don't like Tucker when his rhetoric causes them to settle a lawsuit for over 700 million dollars. This is the same reason they cut Bill O'Reilly, the previous pundit golden boy, he was losing them money in lawsuits.
I think that, combined with upcoming Systemantic lawsuit and his recent video about how we should invade Canada and Mexico to liberate them, was finally just too much for the Fox lawyers to handle.