Not too surprised.
The PED debacle hurt him. The lawsuit seems to be an attempt to get back at his employers for it.
I would be interested to see what the UFC would have offered him, if anything over the next while. To honor the contract they would have to have a fight for him at some point.
I feel badly for the guy. He played the part of a company man for them right up to the failed drug test, but I never felt that the UFC did all they could do to make amends with him.