Was this happened before or after theymos become the sole admin of this forum, I believe previously the admin of this forum is satoshi himself. I always wonder why theymos was chosen to be the admin (since he is not the one founded the forum, --or maybe he is actually the one founded the forum, maybe he is satoshi--)
theymos was the third head administrator, after Satoshi Nakamoto and Sirius. You can see he described how and when he became a head administrator.
The first Bitcoin block explorer was created by theymos two years before he became a head administrator.
Why did he became a head administrator?
I guess it is because he one of first Bitcointalk members and has deep technical knowledge (his block explorer is an example for his technical skills) and contribution for Bitcoin and Bitcointalk communities.
So far theymos is the only people who code the forum.
It's surprising how well-documented history can become totally forgotten... Satoshi created the forum on Nov 22, 2009, and was head administrator until almost 2011. Then Sirius was head administrator until 2012, which is when I took over.