Not really a surprise, Toto Wolff is part of Bottas's management team so that's how he got the merc seat and Massa was being forced into retirement. Williams use the merc engine and now get it millions cheaper for letting Bottas go and once he left that left Williams with the rookie Stroll as their only driver, hence they then needed an experienced driver to retain the Martini sponsorship. There an awfull lot of politics in F1.
Well, I think he'll keep lewis honest. He's not slow, and can hopefully show the paddock how good he is, with the best car underneath him.