Cyborg can read the writing on the wall: her prior, systematic use of PEDs won't fly anymore. She just watched Overoid morph into Overeem and get mauled without the PEDs. she's also not the top dog in the division, and wants to be catered too.
The question is, without Strikeforce, where does she go and get big $, high profile fights?
Dumb move dude.
Oh, and I'm sure the "standing, pee-in-a-cup" drug test thing was a factor too.