The quiet and steady decrease of faith leads to a surrendering to the world. When that happens there are no white flags or formal, public ceremonies marking such subjugation. The adversary cleverly does not insist on these ceremonies so long as the results are what he desires.
A few "sell out" directly, like Judas. Thirty pieces of silver are not necessary if a little notoriety will suffice.
There are many more who are honorable individuals but are simply "not valiant" in their testimony of Jesus.