I've seen it argued before that it couldn't have turned out differently (https://www.cnn.com/2017/11/04/politics/bernie-sanders-2016-...) and maybe that's true. The sad fact is that we'll never really know what could have happened if the DNC had played fair. I agree that young voters don't generally turn out to vote. They also don't generally turn up to campaign rallies but for him they actually did. They showed up in numbers so large that they filled entire arenas past capacity. He often drew crowds much larger than Clinton did and she had the name and the money for paid attendees to boost her numbers.

What I can say is that in that election the country was looking for something different from the government. They knew that the status quo wasn't working for them and that was the only thing Clinton was offering. I know that in the end that feeling was enough to drive at least some people who normally voted democrat to vote for trump (or third party). The fact that the DNC ignored the will of registered democrats and decided for themselves that Clinton was their Chosen One before the primary election was held also caused some democrats to vote for trump or to stay home entirely. I can't claim that the DNC was the cause of trump getting elected the first time, but they sure didn't help.