I don't think there is a design to it. It's just politics has strictly become about 2 parties that purely hate eachother so much it's not enough to just disagree, no they must do everything in their power to do everything so far the exact that everything is only in extremes now. There is no discussion, no agreements, no common ground, no concessions, it's all just purely "our way or no way".
Both sides are guilty of it but Democrats seem a bit more childish about it and when their ideas are distilled down they are all just awful ideas when concentrated.