I think Gerrard realised that we won't make CL anytime soon.
He probably realised this quite a while back, last season came to everyone as a surprise.
Stevie's in his twilight, one last payday and the chance to play abroad - without having to learn a new language, essentially adapt to a new culture & quite possibly pick up a medal or two...
All the best to you Stevie, would've done the exact same thing in his position.