Why Did Hillary Lose?
There is a double curveball on this answer. First curveball; Bad campaigners don't lose primarily because they are bad campaigners. They lose because they end up getting the nomination in unfavorable times for their party, when the shinier candidates sit it out. (Least) bad candidate wins then, and naturally fails to turn it around with already an immense disadvantage going in (W for 2000 is an exception).
What defines good or bad times? The three variables of Time for Change; economy, one-term incumbency for the party (are ppl tired of you?), popularity of the incumbent.
Hillary, not a stellar campaigner, had the nomination during a bad time (Obama popularity, economy were all meager). Mitt, MccCain, Dole, are all in the same category, ineffective national campaigners who ended up with the nomination, McCain after disastrous W for example.
So we could easily blame Obama for the fuck-up. But there is a second curveball; Obama's popularity was not too high, but Hillary, and in the larger sense, Clintonism had something to do with that. Bama 1st term was entirely Clintonite, if we go by SecStates as signs, first term was Hillary second was Kerry. First had war in Libya, second had piece with Iran. Many Clintonites, Summers, that wretched punk Rahm, were all in the first term, gone in the second.
Then the conclusion is Clintonism partially doomed Obama, the dirt spilled on Hillary, who went on to lose the election. It was fitting in a way, poetic justice, Clintonism sinking a Clinton.
"But if people are dumb on politics analytically how could they have connect Clintonism with their bad lot in life?"
They didn't have to. The sins of Clintonism are too numerous to go into here, but after decades of this stuff people finally started to feel it, in their pocketbooks, in their communities. And at every election by simply selecting "the other" because they were always unhappy, they finally landed with the "ultimate other" who was against everything, who happened to run against a Clinton who was dealt a blow which her husband's politics richly deserved.
"But Obama ran and advertised himself as a change agent, why couldn't he do something different?"
He was too young, too inexperienced, without any power base of his own. He had ran against Hillary during the primary, so maybe he thought he had to placate the Clintonites, at least through a cabinet position. These Clintons are a pest; they are rabid networkers, you have to watch your back, you never know how these mo..f..kers can git you... Other appointments, ok.. bcz the credit crisis happened in a system Clintonites were largely responsible for. But then, little here, little there... you start losing your soul.
"How come some people appeared to have a nostalgia for 90s during 2016?"
Some people. And as we know people don't have much understanding of politics. To the extent the nostalgia was justified.. sure, Clintonism had merely started then, the degradation would take decades to play itself out. So in the rough psyche that is people's political mind, such nostalgia could, marginally make sense.