Out of curiosity, where were you living during the 2008 election?
The left wing didn't aimlessly move left away from labor. Biden was dramatically more pro-labor ("New Dealy") than Obama. The right wing lost their fucking minds because we elected a black man. Trump himself is a one-man microcosm of this: loosely Dem-aligned until... Obama.
Spend some time with the GOP base. They're actually broadly racist, ranging from slightly (and ashamedly) to loudly and unabashedly. The left obviously also has various problems with race, so don't take this as some implicit categorical exoneration.
And she's a woman and she's black, again. Then there was the issue that one side of the Democratic party wanted to support Israel more strongly or something, and the other side wanted to protect gazaans and the Palestinians. I think many people wanted to do both at the same time, but there is a fair number of people that picked one side or another. Some of those people voted against her. Some people in my family thought the biggest problem facing America was dei.