I'm almost certain from everything I've seen about Bitcoin over the years that he wasn't a Linux developer who learnt Windows and C++ just to "obfuscate" his identity, he wasn't a non-native English speaker who learnt perfect English just to "obfuscate" his origin. He wasn't a professional cryptographer or even up to date with the latest cryptographic research according to Gavin Andresen[0]. It's most likely that he was indeed a native English speaker and a C++ Windows programmer who happened to be very passionate about digital cash payment solutions.
http://www.emaildiscussions.com/showthread.php?t=57794
Gmx is popular in Germany but I think it was always a bit niche outside Germany speaking countries it was relatively unheard of at the time.
Notably, you might of heard of GMX when visiting Germany for the CCC convention. Both Len Sassaman and Dan Kaminsky presented at CCC in the same year (2007) at 24C3 for example. Dan presented for several years in a row and fiercely opposed Craig Wright’s claims to be Satoshi.
Kaminsky, Finney and Sassaman all died rather young.
He also used upload.ae to share draft of Bitcoin whitepaper[0] and upload.ae was literally unheard of. I didn't see anybody saying they used it or knowing who owned it. My assumption is that it was run by Satoshi's friend or somebody that he trusted.
[0] https://www.bitcoin.com/satoshi-archive/emails/wei-dai/1/
And maybe he didn't cover all tracks....how did he purchase bitcoin.org domain in August of 2008? Some say via cash in mail but I'm not so sure.