Yeh, the safety car timing completely blew their strategy.
Just thinking more about Merc strategy, I wonder if they should have only pitted Lewis? Russell was in 2nd and likely would not have been overtaken, so they would have been almost guaranteed 2nd and 3rd. In fact with how fast Lewis was, they could have got 1st and 3rd maybe as George could have helped him DRS wise. Lewis lost time double stacking too so would have been even closer.
I suppose they genuinely thought pitting both gave them a good chance at a 1, 2 though so that's probably why they did it. Tricky call I guess.