But never did their faith benefit them once they saw Our punishment. [It is] the established way of Allāh which has preceded among His servants. And the disbelievers thereupon lost [all].
So their bringing faith upon seeing the punishment descending upon them, did not benefit them. This is the way of Allah that has been consistent among His servants: that their bringing faith upon seeing the punishment is of no use. The disbelievers doomed themselves at the time when the punishment descended, by having put themselves in a place of destruction because of their disbelief in Allah and not repenting from it before seeing the punishment.