Trump haters keep asking this question, "Why to people still support him?" This is usually accompanied by a list of heinous acts Trump has done and sometimes a list of virtues that the Obamas embodied.
There are some interrelated reasons. It starts back in the early 1990s with Clarence Thomas and Bill Clinton. During his confirmation hearings in 1991, Thomas was attacked as unfit for the court because of accusations of sexual harassment. But then, the following year the Democrats nominated Bill Clinton. Clinton has has multiple extra-marital affairs, before, during and after his presidency. Some of these were clearly worse than anything Clarence Thomas was accused of. His supporters made it clear that they didn't care what his personal life was like as long as he supported the proper policies in the White House (starting with abortion). There was no question that George H. W. Bush was the more upright person but Clinton supporters didn't care. In fact, when his affair with Monica came out, Clinton supporters outright admitted that their outrage to Thomas had all been an act to keep him off of the court.
Once you've admitted that your moral outrage depends on the policies of candidate it's hard to be taken seriously. And this wasn't ancient history. We almost had Bill back in the White House again as First Gentlemen.
And it's not like Hillary Clinton was a spotless candidate, either. The choice wasn't between Trump and Obama. It was between Trump and a Clinton. The list of scandals she has been involved in is far longer than I want to devote space to here. It was bad enough that, on Inauguration Night, 2001, SNL did a sketch about all of the last-minute Clinton scandals with the punch-line "What do you expect, we're the Clintons?"
In addition to having an unsteady moral compass, the Democrats also showed that no one was virtuous enough to escape attack as a racist. McCain was going to roll back civil rights to the 1950s. Romney was going to roll them back to the 1950s and bring back slavery. The two primary attack against Trump, moral superiority and racism, were blunted by overuse.
Many of the attacks on Trump were exaggerations or outright lies and his supporters know it. He did not call the neo-klansmen good people. He did not follow Hillary around the stage. He did not collude with the Russians. It's not racist if Speaker Pelosi attacks the Squad but if Trump does it's a top news item for days (complete with a twisted version of what he actually said). Never-Trumpers seem to believe that the louder they say these things the more effective they are but instead Trump supporters just tune them out.
There's also a matter of policies. Obama's policies hurt a lot of the middle class. He presided over the slowest recovery in history. Obamacare caused a dramatic rise in insurance costs for people who had been buying catastrophic insurance. His middle-east policies were a disaster. He inherited a stable Iraq and, through mismanagement, allowed the rise of ISIS. He allowed Russia to expand. He signed the Paris Accords which would have hurt American industry in exchange for a rounding error in CO2 reductions. Clinton promised to continue or expand on these policies. The current crop of candidates has moved far to the left of candidate Obama.
The Democrats have become the party of heavily urban areas. They openly disdain people who live in the suburbs and rural areas.
So, the question really becomes, "Why don't Trump supporters abandon him and embrace a candidate who despises them and who's policies will hurt them but who is a certified member of the ruling elite?" To ask it that way is to answer it.
A final note on the Obamas: The image we have of them as the ideal couple is a media creation. She hated being First Lady. He didn't like working with people and preferred to go over briefing papers alone at night. Foreign leaders hated meeting with him because it always came with a lecture. He was ultra-competitive, a poor loser and a worse winner. He also had a poor opinion of rural voters, describing the people who preferred Hillary in 2008 as bitter, clinging to guns, religion and racism.