The point is sanji didnt do it on his own like you are trying to act he did. If not for others being around momo would be dead as sanji was caught instantly.
sanji literally save momo, he had to throw momo to shinobu, because if he keep bring momo, momo will be dead because of the height.
1. King want to kill Momo -> failed
2. King want to kill Sanji -> failed
3. Sanji want to save Momo -> sucessfull