First of all, we need to stop with this BS that Dems 'need' Manchin because a Republican would be in that seat. There is nothing in either the US Constitution, or the DNC platform, that says they need a 'Democrat' senator from West Virginia who will continuously ratfukk the party and be drunk with his own power.
Second of all, his own constituents want things like a $15 minimum wage, and certainly a big infrastructure bill. And I sincerely doubt they GAF about a filibuster to get them.
He's not playing things that way to keep his seat. He's doing it because he's corrupt and he already said the quiet part out loud: "The Republicans are my friends. The Democrats are my colleagues."