Here’s one for conspiracy theorists:
When Contador tested positive at the 2010 TDF. USADA through WADA found out about it. They managed to prevent news of the positive getting out while they went to Contador and—again, working through WADA as well as RFEC-- offered to make him a deal if he would talk about Armstrong doping. This was before any GJ testimony, most likely, and before Tyler spoke. At this point, USADA had no one but Landis (who claimed in his book that USADA offered him a very similar deal), and certainly no recent teammate of LA who could be useful in extending the SOL.
The deal was that Bert would confess to a contaminated supplement, and get a reduced, one year suspension. Bert refused, because (take your choice) he had nothing on Armstrong to offer, he was afraid LA would find out and make his life difficult, and/or he still thought at that time he could beat the rap completely (persuaded by sympathetic words from RFEC). Once USADA was convinced any possible deal was off, they got out of the way, Bert’s positive was announced, and normal procedures began to be followed.
This is just the soft core version of the theory, of course

. For hard core conspiracy theorists

, the version is that someone sympathetic to USADA’s case against LA spiked the beef, and/or manufactured the plasticizer positive. If you’re wondering why they didn’t just do that with LA, I don’t believe he gave any samples in that Tour (other than the one all riders give at the start).