They didn't seem to reckon that against representatives who are sent to reflect the will of that same general public. They are not incentivized to contradict their constituents. In particular they do not have the responsibility to represent the demographic of their losing opponent, and in many ways are encouraged to do exactly the opposite.

It may be the best of all bad plans. But it clearly does not succeed in producing compromises. At the very least it relies on some kind of good will between constituents. When you lose that you no longer have a nation.