I think (read 'hope') that Williams are using the Markelov/Mazepin stuff to push Mercedes into stumping up the cash to get Russell into the second seat next year. Really Mercedes need to be spending the going rate either through money or incentives to get their juniors into race seats or else there is the danger they will fade into obscurity.
I get the feeling that Mercedes, the company, is in F1 as a fairweather team. As soon as things get tough, they'll be on their way out.
Anything that points to long term struggles would certainly fit my tinfoil hat theory that they're looking for an excuse to dump the sport.
(I'm not suggesting the people in the team itself don't see the importance in running in F1. The team is run well by people who know what it takes to compete at the pointy end of F1, as well as staffed by the people who put everything they have into running a top flight programme.
Nor am I suggesting that the executives of the company are against F1 either. The F1 team is clearly supported from the highest levels.
I'm suggesting that the powerful shareholders, who just want the biggest possible dividend, might not want their money propping up some spoiled rich kid.)