How much they study varies a lot from student to student. The typical workload was 3-0-6 per course - 3 hours of lecture, 0 hours of lab, 6 hours of homework. Some were more, like Ama95. It worked out to 50 hours a week.
Some students, like Hal Finney, did maybe 3 or 4 hours a semester and aced everything. Me, I did around 50 hours a week. Doing less did not work out well. The PreMeds did a lot more studying.
And then there were the poor souls who couldn't hack it no matter how much they worked, and they wound up quietly disappearing 1 by 1. The ones who needed someone to yell at them in order to work disappeared as well, and so on for the ones who could not manage their time (like me, I almost flunked out before getting my act together).
Yes, we wanted to be there, we wanted to learn the stuff. There was no compulsion. It all came from within. I would have been angry if other students tried to disrupt it for their selfish political purposes. I'm pretty sure the others felt the same way.
This was a long time ago. I don't know what Caltech is like today. I hope it hasn't drifted too far away.
P.S. I liked the way Caltech operated so much that I run the D Language Foundation the same way.