So we go.
I don't know (though I guess ) where you've got that Chernobyl was built in a hurry and with many faults. Fot its time, it was the most modern of its kind. The nuclear energy plant is not a "khruschovka" (a typical 5-story flea-pit), power plant is a strategic point. The best proof of it - blocks were operable until Dec 2000 without any faults.
The brag about "evil and fool soviet agents" I reject as an... errr... Let's call it "propaganda aftermath", ok?
Though, it's true, that the main reason of accident was a "human factor" - a chain of critical errors.
It was an experiment - a test of capabilities of reactor maintenance gizmoes. If you want, I'll try to explain it in details - though I'm not sure that my English is that good for such specific tech info. So, it was an object of this experiment - to bring reactor to nearly critical conditions. Maybe, the idea of this experiment itself was a fatal mistake. But, I repeat, the goal and means of it was so specific, that no any dumb "agent" could even imagine it. It was planned and conducted by a professional reactor crew. Though, anyway, those people made a series of errors bringing things out of control.