Conversation so far:
When did Garry Kasparov lose the chess World Championship title?
The Kasparov-Kramnik match took place in London during the latter half of 2000.
Who did Garry Kasparov lose the chess World Championship title to?
Kramnik had been a student of Garry Kasparov's at the famous Botvinnik/Kasparov chess school in Russia, and had served on Kasparov's team for the 1995 match against Viswanathan Anand.
What was the aftermath of Garry Kasparov losing the chess World Championship title?
After losing the title, Garry Kasparov won a series of major tournaments, and remained the top rated player in the world, ahead of both Kramnik and the FIDE World Champions.
Did Garry Kasparov ever win the chess World Championship title back?
Garry Kasparov announced 2005 that he was tired of waiting for FIDE to organize a match and so had decided to stop all efforts to regain the World Championship title.
Are there any other interesting aspects about Garry Kasparov losing the chess World Championship?
In 2001 Garry Kasparov refused an invitation to the 2002 Dortmund Candidates Tournament for the Classical title

Question: Why did he refuse the invitation?
Self-contained rewrite: Why did Garry Kasparov refuse the invitation to the 2002 Dortmund Candidates Tournament for the Classical Title?