A million things led to her defeat, including, as some Democrats like I and Rock have repeatedly pointed out, the fact that she's a terrible politician.
However...
Don't sleep on the power of fake news propagated by social media. It's probably a lot more powerful than we are comfortable giving it credit for.
This is a legitimate problem. And most of us like to think we are immune, but we probably are not. To summarize something I said in another venue, I'm fairly certain (now; I wasn't then) that some of the people and groups I interacted with in the Bernie movement online were fakes. They were overly concerned with convincing liberals not to vote for Hillary. And I was arrogant enough to proclaim my immunity by pointing out that, when push came to shove, I still voted for her.
But the fact that it didn't work in this election doesn't mean that it
couldn't work. The fact of the matter is, we are all much more easily persuaded than we'd like to think. That's why advertising exists. Most of us pretend we are the exception that isn't tricked into changing our behavior at the behest of a TV ad, but companies wouldn't spend $200B in advertising in America each year if it didn't work.
The science of how to convince you to behave a certain way against your own preferences is far more developed than you'd like to know. No matter how stubborn and independent you think you are, there are probably dozens of times each day when your behavior is modified by media you've consumed without your realization.
Fake news on social media is going to continue to be a powerful tool for influencing voter behavior moving forward, and laughing it off is not the way to address it.