They knew they could never finger him individually, so they had to team up.
Being turned in by your teammates like this must feel like a massive violation. But if these allegations are true, we don't really feel sympathy for anyone, whether they're the fingerer or fingeree. Lance may well have convinced the whole team to do 'roids with him so that it would be harder for them to rat him out, but take 'roids they did. Or eleven people are lying for some bizarre reason to destroy their entire team's accomplishment and their friend and leader. That would be way beyond fingering though. That would be f***ed.