People were sick and tired of being told what's best for them by a bunch of smug and condescending but out of touch liberal elites, so they voted in a charismatic but clueless and egomaniacal blowhard who wrecked the smug political dynasties but is proving to be a danger to himself and others in the process, and is getting frustrated with all of the blowback he is receiving, because he apparently thought, despite all evidence to the contrary, that he was being elected king, rather than the largely ceremonial figurehead of a democratic republic, much of which doesn't actually like him very much.
Now the question is whether the two parties can come together and behave like adults and create a reasonably effective and bipartisan government once the president is removed under Article 25 sanctions, or whether the Republicans will continue to follow Trump along his downward spiral, while the Democrats choose to put a gun-hating Sunni Muslim who got his pilgrimage to mecca paid for by a Muslim Brotherhood front group in charge of their organization, and the American public begins to really hate both parties.
All most of us want is single-payer healthcare (or healthcare of some sort that's readily affordable to families and small businesses), prospects of a decent career that's not going to be wiped out by automation or outsourcing, and a sense that America has a chance of being a democracy and not a plutocracy again.
Sorry, that wasn't really ELI5, but more of a rant, so here goes the ELI5 version:
See Timmy, America was tired of people who were smart and pretended to care about poor people but were really mean and rich, so they voted in people who pretended to be dumb but were really mean and rich and clever in a different way, and now we wait to see if the mean people will decide to be nice, or if we just have to deal with different flavors of meanness going forward.