So why didn’t they?
Because they didn't have a majority in the last two years.
Do you live in the US? The first half of the Biden administration was hamstrung by Manchin, Sinema, and the Republicans. The Democrats had nominal control of the presidency and legislature but faced implacable resistance from the Republicans and these two nominally Democratic senators. Until the recent Supreme Court decision the US hasn't had a king.
And Manchin had no real chance of reelection anyway.