Generalized, this looks to me like a question about why humans sometimes get hell-bent about some idea and become blind to the side effects and ignorant when it comes to risk management.

Sometimes it could be malice or personal gains. Sometimes, I think, it could be just a strong bias towards some idea that causes a mental blindness. Such blindness can happen to anyone, at any level of power (or lack thereof), politicians are not unique in this - the only difference is the scope of impact due to the power they have. And we aren't particularly filtering them against such behavior - on the contrary, I feel that many people want politicians to have an agenda and even cheer when they put their agenda above the actual reality, any consequences be damned.