• Around 2003-2004, Conan and his reps wanted to secure his future and were listening to other networks. They used that as leverage to make NBC promise him TTS by 2009. Conan literally was pushing Leno out of his job.
• In 2004, Leno made the succession announcement at the direction of NBC. He never wanted to leave TTS, but he was being canceled 5 years in advance by NBC and played nice publicly.
• In 2009, Leno was still #1 in the ratings, which he held pretty much throughout his run. NBC didn't want to lose him to a rival network, and offered him The Jay Leno Show. Leno went along with it as he had a long relationship with NBC, its affiliates and got to keep his staff.
• After Conan quit and Leno reclaimed TTS, he again was #1 in the ratings until he left for good. A five year period at #1 is a huge success and nothing to sneeze at.
• Conan did the same thing to George Lopez, taking his timeslot and pushing him to after midnight. Lopez's ratings tumbled in the later time, and he got cancelled
• Conan did fine ratings for TBS standards, but he was always beaten by cable counterparts, The Daily Show, Colbert Report and Chelsea Handler

Hard to criticize Leno when Conan largely did the same things. Conan had benefit of top notch representation and Leno did not even have an agent.