Sometimes loyalists to the previous regime who were brave enough to continue to speak the truth as they saw it found themselves exiled or like Trotsky, facing the business end of an icepick.
As far as we know President Trump hasn't started issuing kill lists for American citizens who cherish President Obama's legacy. Not yet anyway. But President Trump has been on a significant rampage to wipe away most of President Obama's initiatives or accomplishments.
Just off the top of my head the Paris Climate Accords, the Iran Nuclear Deal, Obama's rejection of the Keystone XL Pipeline, and the EPA Clean Air Policy are all dead. Obama era initiatives or directives on fair housing, college sexual assault, disparate racial discipline in elementary/high schools, affirmative action, and fuel emission standards have all been reversed or are pretty clearly withering on the proverbial vine.
President Obama's signature achievement, the PPACA or ObamaCare, survived Republican direct legislative attempts to kill it, but has been suffering the death of a thousand cuts legislatively and via the executive branch. Trump first came to serious political prominence by repeating the racist lie that President Obama wasn't an American. President Obama turned the other cheek on this until one night at the 2011 White House Correspondents Association Dinner he let Trump have it with what amounted to both barrels for the otherwise congenitally conflict averse Obama.
Trump can't command people to remove Obama's name from the history books or destroy his libraries or likenesses, but I think he would if he could.
And yet for all of that three times as many people listed Obama as their first choice for best President of their lifetimes as those who listed Trump. In fact Obama received the highest score of any President.
President Donald Trump doesn’t like to talk about polls unless they’re good polls. So it’s unlikely that he’ll bring up the latest survey from the Pew Research Center, which says that more Americans consider Barack Obama the best or second-best president of their lifetime. Trump comes in fourth, behind Bill Clinton and fellow Republican Ronald Reagan. But he did beat out both Bushes — not even two years into his presidency.
The results of the survey do tend to skew toward more recent presidents, given the age demographics — which is why presidents like FDR, John F. Kennedy, and Dwight D. Eisenhower, who often end up in the top of the all-time presidential lists, didn’t make the cut, and for whom only silents and some boomers can vouch for these days. (Pew surveyed 2,002 adults between June 5 and 12 for this poll.)
Trump may become better liked over time though I would doubt it. He definitely has changed things. He has a better shot to be remembered as transformative than likable, which isn't necessarily a good thing. Destruction is a kind of transformation as well. But the wholesale liquidation of Obama's works is an odd counterpoint to the fact that a sizable percentage of people consider Obama to be the best President of their life time.