Suspect the cost of replacing Checo with ending his contract and his sponsorships this early was too expensive even if it costs them the extra money that 1st place in the constructors would bring. Would not surprise me if they have some performance clauses that means they can bin Checo off for cheap by the end of the year if he carries on under performing.

Also suspect that they know who they want next year as well as Carlos choosing to sign for Williams on the same day cannot be a coincidence. They have to be really sure that Max isn't going to Merc next year now as none of the other available options would be even a close replacement for Max.

Merc not signing Max would mean Merc signing Antonelli for that second seat now as Carlos is also not available, shutting the door to Max for 26 as well as they would be unlikely to drop Antonelli or Russell once signing them unless they have an absolutely terrible 25.