I've always thought that younger people (especially of the current generation) are becoming less religious and more secular. They seem to nearly unanimously support things like gay marriage and are turned off by the GOP's crusade against it. I believe they turn to the Democrats because they feel that the liberal position on social issues is more with the times. A lot of people seem to vote for any Democratic candidate purely for this reason.
I don't think the younger people understand economics or follow politics closely enough to understand that Rand has more socially liberal positions on things like gay marriage.
If you ever try to talk politics with the average 20-something, you will find that they know very little about foreign policy, economics, the law, etc., but have firm stances toward things like gay marriage, abortion, stem cell research, evolution theory, and feel that the Republicans live in the stone ages.