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.
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.