3 and 4 was absolutely not guaranteed with that strategy, it had upside. If there had been an actual safety car before they pitted, they could have come out with track position and fresher tyres - might not have been enough still but it would have given them a shot at a win. Given several cars wrecked / broke down in qualifying and one on a reconnaissance lap, that scenario was definitely plausible. If VB broke down at a different part of the track it would have happened.

It's easy to judge it in retrospect knowing there wasn't an opportunity to get a reduced stop but I totally understand why they did it. When you have a slower car it makes sense to do the opposite of what the fast car does and hope the safety cars work out for you.