I don't know why you keep mention this strategy calls based on rules and precedense. No matter what decision RD would make, merc would do excacly the same thing which was not to stop Sir Lewis.
But lets analyse this:
Latify crashes, SC out, at this point nobody's know if they will manage to restart or not, Max 10s being Sir Lewis who passing Latifi's wreck and approaching last corner, at that point he knows he is screwed and this, what would appear as easy win start slip away. If they pit, Max will stay out and they will loose track position, if race does not restart game over for merc, if they restart it would be down to Lewis to pass Max so merc do right call not to pit.
Max then pit as he would do opposite to what would merc do, they have to gamble.
At next lap cars are much closer together and if merc decide to pit they would lost not 1 but potentially more places so merc do right thing not to pit again. From now on only thing merc can do is pray so the race will not reatart, sadly for them that was not the case.
Those decisions were the only logical decisions they could make regardless of what RD or other stewards would do and what regulations state.
Merc was simply very, very unlucky.
IMHO wrong decisions has been made earlier on. I think merc should keep Lewis out when Max pit 1st time. They had approx 6s gap so they could easily run at least 2-3 laps. With Lewis pace there was high chance that he would be on par even on slightly worn tyres. This could play to his advantage later in the race, and if he would be way to slow they could bring him in next lap so no harm done. But they did not even tried that.
Second wrong decision was not to pit under VSC later in the race but this was bit more riskier as redbull could take track position at the time but then Lewis already complained about the tyres.
This is the type of races I want to see where emotions running high, adrenaline level are sky high there is excitements and drama, and I don't care who came victorious at the end. On this occasion was Max, but next time maybe Lewis or even someone else. I already looking forward to next season and to see how teams are prepared for quite a big changes to the car.