Originally Posted by
Kyan
I think A_Magical_Unicorn_Rider means that, towards the end of 2.0 and during 2.1's story line, it is said (by fellow Scion members) that Thancred was overworking himself to prove his worthiness: Thancred was trying to make up for the lack of Louisoix, in a sort of attempt to fill their former leader's absence. Makes sense given what we have learned about Thancred in 2.2 - he owes a lot to Louisoix, it seems.
It was this emphasis on being the best and working so hard that lead him to being susceptible to being possessed by Lahabrea.