I'm not blaming the parties. They are doing the minimum to get by. That's human nature. I'm not sure how people didn't know about Bernie. I didn't have an intimate knowledge of all his positions, but I knew who he was and what he was about several years ago. What seems absolutely absurd is the notion that we can't be upset with the process the parties have created to ensure we can't effectively do the bold. Ultimately, the parties get to pick who they want. The primary voting events are window dressing. In the end they don't have to go with what primary voters say.
No, they don't have to...but if that were really true, that they
get to pick who they want, then Obama would not have won the nomination in 2008. Hillary was, as she is now, the establishment candidate. Yes, in theory, the super delegates could override the popular vote and delegate count from the primaries/caucuses, but that didn't happen in 2008 and since the current rules regarding super delegates were adopted in 1984, they have not ever decided the Democratic Party nominee.
If Bernie somehow pulls off a miracle and wins 59% of the remaining delegates and goes into the convention with more votes/delegates than Hillary, I doubt the Democratic Party would deny him the nomination with the super delegates. It would cost Hillary the election. The same holds true for Trump and the GOP if he is close to the majority threshold.