He was a symbol of a lot of things.

First, racial unity. Now that we’ve had a black President, it’s hard to express how unfathomable that would have been even 20 years earlier. The majority of Americans became okay with interracial marriage in 1995. We went from “you can’t even use the same water fountain as me” to a black President in two generations. Considering the role of racial tensions in disrupting peace in the United States (and the history of fanning the flames for propaganda during the Cold War), this was a major victory.

Second, he was the possible end of American adventurism. Bush was basically despised by virtually everyone around the world. He was considered dangerous because he was the sort of guy who would start a war to benefit America even if it negatively affected everybody else. America was special and therefore we got to decide. He didn’t have and very deliberately did not seek the approval of anybody but his own American GOP buddies. He was considered both a slick salesman and a buffoon. Obama sought out and repaired our relationships with our allies and friends even before he was elected. He deliberately downplayed exceptionalism language. This was derided as an “apology tour” by Republicans, but it was very much appreciated by the people who give Nobel prizes.

Both of these things sustained heavy backlash in the 2016 election.