Because they figure if they can shuffle the deck chairs fast enough then nobody will notice that the ship is sinking. Sure, their shitty behavior eventually catches up to them, but they can keep calling out to "pay no attention to the (wo)man behind the curtain" for a while, and sometimes they can get away with it and things will blow over. In this case, her shit had already hit critical mass and they can't hid her any longer. Chances are good she'll quietly disappear for anywhere from a few weeks to a few months, and then pop back up on the radar at another company after making some sort of nonpology over her previous behavior.