DoD voters are a fair mix of pro musicians, regular listeners and casual listeners. And everyone has different preferences in production quality, music genres or even game selection. But in the end, because we do have a decent amount of voters, all those different preferences and biases cancel each other out.
It all comes down to this: what sounds good to most people will place higher. Nothing complicated about it. If the DoD voters were all thinking along the same lines, we'd be having a single game/series or a single genre prevail every month. And that would be terrible.
So, just because DoD rankings don't align with your personal preferences, doesn't mean they're bad rankings. It just tells you about the diversity of our voter base. Now, enough complaining, start working on something for Pinball Month guys.