Chernobyl was caused by putting men who didn't understand nuclear power in charge of building and running the largest nuclear reactors in the world.
Actually, the RBMK reactor had dangerous design flaws, that were completely unknown to the operators. The rods that were intended to stop nuclear reaction, were designed in such way, that they actually accelerated the reaction for a few seconds. That was the immediate reason for the explosion.
On some other stations equipped with RBMK reactors, the flaws were already encountered by the operators, but no modifications to the design of the reactor were made until the catastrophe.
Off-topic, but sounds weirdly familiar in this thread's context...