okay if they need 60 votes to do cloture on the filibuster vote what good would it do tho get Manchin on board you still only have 51 votes!!
The whole premise of the so-called "nuclear option" is that the Senate rules can be changed by a majority within a session (as opposed to at the beginning of a session. It's not clear if this is true, when Hubert Humphrey was presiding over a 68-32 Democrat majority Senate he ruled from the chair that the rules could be changed by a simple majority within a session, his ruling was appealed to the floor and he lost 48-52.
Of course, 1967 Democrats and 2021 Democrats are different animals, but it is still not a simple matter of Roberts Rules.
A single US Senator is the most powerful parliamentarian in the world BECAUSE he has the filibuster, and yes, Senators in 2021 are much weaker and much more corrupt than they were in 1967, but still, voting to make your own self less powerful for no good reason may not gain 50 votes, even in THIS Senate.