She didn't offer the voters the reason why they should vote for her. Her message was "I'm the best candidate"! Really? Why are you the best candidate?

The real reason why she lost (electoral college aside) is that she didn't have a clear and concise positive message, and easily understandable goals.

Saying "I have the best chances against any Republican candidate" during primaries and "I'm better than Donald Trump" during election campaign is not enough.
Alternatively, the perception of these problems demoralized the public. In tactical terms, we assume that Clinton cannot simply exchange herself for another person entirely, so the perception of "baggage" came to weigh her down regardless of the merit of the discourse. In the end, most people voted in apathy toward "status quo", not with a specific desire to up-end it.

I think that she asked and tried to answer the wrong question - why I lost?
What is the right question?