(1) This wasn't some recent trick intended to help Hillary beat Bernie, and

(2) The Democratic Party's nomination system is still way more "democratic" than what existed within my lifetime.

A longer explanation follows if you're interested:

Democratic presidential nominees were not selected by primaries until the late 1960s. Primaries had been created during the Progressive Era, but they mostly were not binding on the state's delegates, who tended to be party insiders more focused on winning than on ideological purity. In other words, in a way the system was built from superdelegates.

One reason the student activists and other leftists were protesting outside the 1968 Democratic National Convention in Chicago, getting beaten and teargassed by cops working for a Democratic urban machine, is because the party insiders were about to nominate Hubert Humphrey (tarnished through guilt by association with Pres. Lyndon Baines Johnson) even though many activists wanted a staunch opponent of the Vietnam War (originally Robert F. Kennedy but, after his assassination, Eugene McCarthy). Humphrey hadn't even bothered running in the primaries.

The embarrassment of that clash between the left-of-center party and the leftist activists convinced many Democratic leaders they needed to open up the delegate-selection process to get some of that activism and diversity reflected inside the convention. Making the primaries binding, as the McGovern-Fraser Commission did, put delegate (and therefore candidate) selection in the hands of the most-motivated party activists, and they quickly compiled a poor track record: McGovern crushed in 1972, Carter coming from outside the party organization in 1976 and then having an embarrassing one-term presidency during which he fought with the Democrats in Congress, then Reagan (at the time considered an arch-conservative) beating them in 1980 after their delegates broke into an embarrassing convention fight over the party platform.

So the Democrats decided they needed to increase the influence of Democratic leaders from each state who were more likely to have long-term career interests in the health of the Party. They scaled back the excesses of the experiment with democratic delegate-selection mechanisms, and through the Hunt Commission carved out a role for ex-officio superdelegates.

https://en.wikipedia.org/wiki/Hunt_Commission

In sum, the purpose of the superdelegate rule was to increase Democratic successes in presidential elections. It reflects a common-sense belief that Democratic voters would receive better representation from Democratic presidents, even those nominated through impure methods, than they were likely to receive from Republicans.

Cooper, Alexandra L. 2001. “Nominating Presidential Candidates: The Primary Season Compared to Two Alternatives,” Political Research Quarterly 54 (4): 771-793.

Kaufmann, Karen M., James G. Gimpel, and Adam H. Hoffman. 2003. “A Promise Fulfilled? Open Primaries and Representation,” The Journal of Politics 65 (2): 457-476.