On page 10 we see him notice the explosion while he's flying near the area
Shigaraki has always been a one touch win power but the difference now is that his durability is far beyond everyone in this manga to put where it's very questionable on how they're going to beat him, Deku and S&S have the luxury of having quirks that he wants so he at least won't use his decay on themTo be honest, because of Shigaraki's quirk how can anyone close combat fighter beat him? Even before this power up, one touch and it's game over. Shouldn't his decay work on everyone?