should the other candidates clear out to make way for biden?

no.

these results don't strengthen his argument at all - they've demonstrated that his support amongst black voters was overrated, and he has yet to demonstrate that he can generate support amongst key white swing demographics.

south carolina will not be in play in the general, and the argument that black voters in milwaukee (somewhere that is in play) will vote for him because he won south carolina is just racist, and probably totally wrong on top of it.  

they should force biden to win a state that has swing demographics and will actually be in play before they get out of the way - a state like new hampshire, or nevada.