Mercedes had to assume the rules and established procedures would be followed. If they'd changed tyres, there's a good likelihood he'd have fallen behind Max, with the expected outcome that either the race would not restart or that it would restart without lapped cars being permitted to unlap themselves. In either of the predictable cases, it made the most sense for Lewis to stay out on his old tyres.
As with *everything* you've posted, this is a non-argument.
How the hell did Mercedes know that SC will be out all the way untill lap 57 though?
Maybe the debris would be cleared on lap 56 and they would be in trouble either way. Also I don't really get why people are angry that only some lapped runners weren't let through, but if they let all of them it wouldn't change the end-result. If he let all of them pass, then you would say rules have to be followed and they should finish behind the SC, I agree but the track was clear, and we had a chance to finish the championship under green flag, and Masi took that option (but he stupidly also allowed some cars through that ironically were between Lewis and Max which polluted some people's minds and they started to think it was rigged).
My point is, if he let all of them through I would't be against that decision at all because if the track is clear and it's a specific situation that you only have 1 lap remaining in the season but the rules imply that the lap has to be finished behind of the SC, just because lapped runners can catch the queue, but as said, it's the final lap of the championship and the track has no debris, green flag it for Pete's sakes.
And Mercedes did take a huge risk for staying out 40 old hards, they certainly didn't know that the race won't be restarted hence Hamilton swearing all the time on the radio when the SC was deployed, they just took a risk and it in the end that risk was partially the reason why they lost.
It's just not Masi's fault and stop making it like it is, Mercedes were greedy and wanted to play it safe at the same time, and it backfired.
Unfortunately we will talk about this all the way to Bahrain, hopefully some repercussions are decisions will be made and, firing people won't solve the issue, and frankly I think Masi didn't make the decision on his own, maybe Liberty or FIA were involved as well and that's why they are trying it so hard to cover it up or make it look like it isn't a big deal, so blaming it all on one individual is foolish.