Toji fucked up in the last moment against Gojo, regardless.

Had Gojo died there, he'd come back as a curse.
He lived and came back as the Strongest.
This would only happen if Toji didn’t kill Gojo with cursed energy/cursed tool.

For all we know that knife he stabbed him in the head with (not the ISOH) is a cursed tool that does bumble fuck
 
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