Stuart

It's possible we have another small time skip coming up where they all (or some) learn this technique or haki that cancels out the immortality. I feel it's kind of a given at this point that chopper, robin, nami and ussop gain some kind of buff I see Brooks and jinbe getting there upgrades last like right before the final war or during

I mean it makes sense he let his guard down. He was fighting someone who actually was giving him some kind of challenge then it went from a 1v1 to a 1v2 then 1v3, he destroyed and repaired his brain multiple times also he was doing things he normally never had the chance to do, he was definitely worn down and tired then sukuna pulls out a binding vow for an instant wcs (if I remember correctly) of course he let his guard down if he didn't realize sukuna managed to copy mahoragas technique gojo may have been the strongest but he was still human at the end of the day