I don't like what Williams has to put up with, but, hey, money is money - and Williams needs it badly. They lost major bucks with HP pulling out of F1, and when they parted ways with BMW!
So, Narain might be bad (or, not as good as others), but he brough in TATA as the sponsor, and if Toyota will give them engines for free in return for a place to develop their driver, then, if i were FW, I'd say "so be it!"
(perhaps that is the reason why I'm not Frank Williams

)