The slow corruption of ideals of the Democrats makes sense if you see making hay as the point of the whole thing for many (not all) people. Some people– many of the base– believe that supporting the ideals and trying to fix problems is what the party or group is actually trying to do. But even they have to be pretty sharp to notice how political priorities subtly steer idealism away from politically unprofitable solutions, and frequently stop being a source of energy once the reputation for trying has been established.
The hay that they’re making takes different forms, of course. Sometimes it’s votes, sometimes it’s grant money, sometimes it’s a feeling of moral superiority. But sooner or later they run out of grist for the grievance mill, and then they have to start putting other stuff through. And that’s when the bullshit begins. That’s when the tail comes to wag the dog. That’s when the process becomes more important than the result. This happens on the Republican or conservative side too, of course; military spending is hay.
I suspect that if he exists somewhere, Martin Luther is having a quiet chuckle at the universality of human nature, because the capture and deterioration of moral institutions is exactly the circumstance he fought against.