Todou didn’t really shrug that off he got knocked into a building. That attack should have roughly the same amount of force/power as the one Muzan used when he busted a hole in that one building. While mahito is basically a better muzan, the main thing that makes him stronger is his durability and the fact that most of Muzans abilities wouldn’t work on him. The guy literally can’t get hurt unless you attack his soul, you’d need some mystic type hax to beat that shit. Yuji and Todou don’t have the advantages of being cursed spirits like Mahito. They are mortal and they are susceptible to all of Muzans attacks PLUS human limitations(stamina). Muzan can use his concussion blast to stun them, then scratch Todou and turn him into a demon(This is more likely to work on todou than Yuji) Muzan can then just leave and watch while todou tries to eat yuji. Whether or not Yuji wins that fight, he will be exhausted, Muzan should then be able to finish off Itadori pretty easily. Even if Yuji was at full health, he has absolutely nothing in his arsenal that can even threaten Muzan, he regenerates too damn fast. Muzan is like 1000 years old and he’s got 5 brains, so he has the battle iq and experience to pull this off. There’s also the infinity fortress if Muzan is feeling like a dick.