You can thank Ruth Bader Ginsberg's arrogance for part of this. Obama asked her to retire in his last term so he could nominate a new liberal justice and she refused. Instead she held on and died at 87 while Donald Trump was president allowing Trump to nominate a Conservative justice and stack the court.
Now I know that even if that had of happened, the vote would have been 5 to 4 in favour of overturning Roe, however, if Obama could have managed to get Merrick Garland appointed in the last year of his last term, it would have flipped.
The problem is that being a Supreme Court Justice is a lifetime appointment.
Donald Trump nominated 3 young Supreme Court justices. Age 50, 54 and 57. He changed the political makeup of the Supreme Court, potentially for the next 20 or more years.
It all comes down to the power of the Senate since the Senate approves the nomination. And the Senate votes right down party lines. If the DEMS don't control the Senate, they have no control over who sits on the court.
And Biden is on track to lose the Senate.