Allied Reinforcements are in-fiction ways to adjust for difficulty on the spot by helping the PCs in a way that doesn't look obviously too much like you're just handing them a W. The Reinforcement Power Confusion in the Ranks negates Tension for all Enemies which sounds like what your PCs needed there.
Having said that, I think letting people fail is also part of giving them agency. If you gave them multiple shots at getting out, and they choose to stay, they should be allowed to do so and to deal with the consequences of that. Live Another Day makes the consequences entirely narrative, rather than mechanical, and even after that the Plot Armor rules make it so that they can simply be hospitalized after ejection instead of dying horribly when their mechs explode.