No, Hillary's "mistakes" didn't cost her the election, Trump made his own mistakes.

People in the Hitlery Rotten Cunton camp like to say she lost because she ignored Wisconsin, barely campaigned in Michigan, didn't talk policy much, etc.  Don't get me wrong, these were mistakes, and they did hurt her with voters, but it's not as if Trump didn't make his own mistakes.  Here are some examples.

Stop and Frisk

Prior to this, Trump had been polling 18-20% with Black voters for about 2 weeks straight, which is near impossible for a republican to do.  After this, he dropped to 5, and didn't come up much from that.  Sure, the exit polls on the 8th may have underestimated his actual vote, so maybe instead of 8%, he got, say, 10-12%, with a lot of Black Voters staying home because they didn't like Hillary either.  And yeah, that's much better than republicans before him, but it still didn't reach the level it was through most of September, after "Stop and Frisk" this was not possible anymore.

For full context, Stop and Frisk is largely seen as a racial profiling, racist cop tactic.  It may not be, and I'm certain Trump didn't mean it that way, but that is how it was seen.  And expressing intent to use it in minority neighborhoods (even if not exclusively there) was just NOT a good idea.

Muslim Ban

Granted, this spiked his PRIMARY poll numbers, at least in the immediate sense.  However, it was also used as propaganda to paint him as a bigot, even in the primaries.  And in the general election, it had a much more pronounced effect.  Sure, he minimized the damage by pivoting to Extreme Vetting, but if nothing else, it still served as Confirmation Bias about his alleged "racism" and "bigotry", plus, it's kinda hard to NOT see it as Islamophobia.

Sure, there's reason to believe that Islam hasn't ironed out its problems as well as the older religions have, and this no doubt started that conversation, but this is about whether it costed him votes, not whether it started a needed conversation.

Failure to reach out to gamers

Sure, there's that infamous 2012 tweet, but compare it to Hillary's entire anti-gamer history, now add onto that her embrace of Brianna Wu, her endorsing the media narrative that GamerGate/Gamers are misogynists who harass and rape women, and the fact that Anita Sarkeesian endorsed her.  Trump had a MAJOR opportunity to win the youth vote, by a WIDE MARGIN, he failed.  Granted, he still won more of the youth vote than most republicans, but still, 65% is better than 45%, no?

Failure to make a "Regressive Left" Speech

Granted, after Hillary's Alt Right speech, this would have been seen as tit for tat, but that probably wouldn't have mattered much.  Painting Hillary as Regressive Left would have been a LOT easier than painting Trump as Alt Right.  Not to mention, the Regressive Left, unlike the Alt Right, is actually ruining lives and and even getting people killed.  To the former, he could have cited examples of people railroaded by the media's SJW talking points, who lost jobs, and in some cases, went to jail on the "Listen and Believe" mentality for stuff they are NOT guilty of.  How many Gamers and Frat Houses have had their lives ruined over the last 2 years?  To this, he could have persuaded the public on why Opening the Libel Laws would be a good thing.

To the latter, most examples are from Europe, but they are there.  Plus it's NOT like Regressives didn't defend the Mateen family.

So what did cost Hillary the election?

Here are the reasons:

1. She was an SJW.  Sure, Trump didn't exploit this weakness very much, but it's not as if it helped her.  Many, including myself, voted for Trump based on this.

2. Trump didn't tow the party line, Clinton DID.  This made her look like a typical, partisan hack DC insider.  You can simplify this by saying "status quo", but there's more to it than that.  It's not just that this was status quo, eating every day is status quo, but nobody cares about that.  It's because these are the specific aspects of the status quo that people hate, and she went full bore on these.

3. WW3 posturing.  Yes, the average American doesn't like Putin, but it's doubtful that a whole lot of them want war with the guy, Russia isn't some small, 3rd world country that we can just bully, and Americans are well aware of this.

4. She ran a "California" campaign.  And sure, assuming she didn't commit massive voter fraud, which is doubtful, this won her the popular vote.  But, rightly or wrongly, the president isn't elected that way.  Trump countered this with a Rust Belt campaign.  This didn't hurt him much in the red states due to his running as a republican, but allowed him to take blue states from Clinton.  This was likely his plan all along, and she fell for it, hook, line, and sinker.