Harry Potter's World is Insecure

If one Voldemort can do it, another Voldemort can do it. 

Honestly it doesn't look that hard. Doesn't take a genius of sabotage. 

The Ministry has to win every time. Voldemort only has to win once. They're doomed, it's merely a matter of time. Rowling only has a story because the Ministry won't secure its shit. Rowling also only has a 'happy' story because she stops there (aposiopesis) and hopes everyone stops thinking with her.

By the way, story of Voldemort: he kills himself with a spell rebound due to violating an obscure wizarding technicality, then comes back to life so he can kill himself with a spell rebound due to violating an obscure wizarding technicality. 

Female writer; naturally the plot, with all its sharp, un-cozy points, is not a strong suit. Nor the "hero" having, you know, agency. The school and its procedures and knick-knacks are what Rowling is good at. (So, taking care of kids and their environment. How bizarre and surprising. Who could have predicted this.)

Without Voldemort committing Canadian Healthcare, Rowling's wizarding world has no chance. What if one of the Wizengamot happens to secretly already be a dark wizard, and decides he's tired of red tape? Game over. 

Rowling's world needs a big strong man to save it from itself. 

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Rowling's world is unconsciously inegalitarian, and has the dark mirror of the problem of the real world.

The Ministry always wants to decay into the Imperium, explicitly privileging noble blood over muddy magicless common dirt farmers and their ilk. "Yeah, uh, we really are better. If there's a dispute, we're probably in the right, you barbarians." Has to fight savagely against purifying its own principles, and will inevitably lose. 

The Global Loser-Egalitarian Empire (GLEE club) has to fight savagely against decaying into pure Marxist Communism, meaning everyone starves to death, and will inevitably lose.