I think the fact we were after Doku and there were some other names in the bag too before Doku got the green sign, made him think that Mahrez's gametime will be allocated elsewhere. I very much doubt he would have been getting as much gametime as an academy young player as Doku is getting now albeit thats also down to Grealish unable to get going at all with various injuries and bad form. (and also KDB's long injury which moved Foden centrally a lot more that originally it would have happened opening up more game time on the wing.)
game time is not even an issue as he is Chelsea's main man pretty much, I bet his salary is much better than he was on here and his agent easily can ask for a contract upgrade after a debut season like this. may as well be pushing soon for a transfer to a CL club using the financial turmoil at Chelsea to his advantage.
without his goals/assists/general play Chelsea would very well be fighting vs relegation.