The five each took a path to clear. They had two each to clear of any guards hiding there and release any potential allies or cannon fodder that could be useful for their mission.
Though they brought a lot of cannon fodder, most of them died while breaching the defences. The prison's defences were very high, and they didn't have enough time or resources to bring sufficient attack power to breach them without incurring significant losses.
Additionally, they sought to create enough chaos to facilitate the completion of their mission.
Although they have cut off communications with the outside world, there is no guarantee that no one might suspect something is wrong with the prison.
There might be regular communications with the outside world, or at least that's what the Big Three told others at the start.
As the four started to clear the path of guards and open doors, they began to think.