Both parties are rotten – how could they not be, considering the complete infestation of the political system by corporate money on a scale that now requires a presidential candidate to raise well over a billion dollars to be competitive in the general election. It's not just the corporate money either, there are hundreds of lobbying organizations for special interest groups.
They had elections in USSR and Nazi Germany too, with candidates that where chosen by the people that really ran the place so no matter what person won, their man was in power. I'm taking extreme cases but there's essentially the same thing going on.
Most people simply let their friends, co-workers, talk show hosts, and the propaganda (funded by the powerful) tell them how to think and how to vote.
Something like half the population won't even read one book per year. Of the other half, how many actually read anything enlightening or educational rather than just recreational.
I will say however, the masses deserve more of the blame just for being so stupid and gullible that they can be deluded into believing that what is so obviously NOT in their own self interest actually somehow IS in their self interest and believing that the rich and powerful elite actually care about the welfare of the masses. With just a small investment of time and effort almost anyone can learn what is really going on, but only a fraction of regular people do.