Basically, the planet becomes uninhabitable by humans, so about 5-10,000 people live in an orbiting space monastery, with vast gardens + libraries and little tea shops that have windows permanently fixed upon a view of the stars, etc. So everyone could devote themselves 24/7 to their studies. Periodically someone would suggest that a team be sent down to determine whether the earth could be re-settled, and everyone would say why bother, we haven't learnt our lesson yet.