Geth founded the Orain (now Miraheze) branch of ATT with two ex-tropers named Brent Laabs and Robert "Bob" Schroeck, who were cast out of TV Tropes for protesting the censorship purge done by Fast Eddie, feeling the purges done in 2012 had fatally compromised the site mission of troping all media.
Brent was tossed out on trumped up bullshit charges of harming their site by doing a site rip of the content with a bot (which is like claiming the same shit Google web crawlers do all the time is dangerous), and Bob was one of the first members way back from 2004 who raised a massive stink about how TV Tropes had sold out and was banished for his trouble (he's an IRL anti-censorship advocate, including being willing to go to court to fight it).
Geth's history is a bit vague. By his own account, he was around back when you could still edit with IPs, but has been very careful to keep his powerword off the internet, and his social media presence is, by his own admission, carefully tailored to make sure that never happens, but he got to know Brent because he took over Wikia's former halfassed ripoff of TV Tropes (there is a post on Geth's blog that explains this in more detail) and started fleshing it out with Brent's site rip, and partnered up with him and Bob to found All The Tropes on the now defunct Orain.
On Orain and later Miraheze, Geth has been very public about his desire to avoid being a dictator (that Legion avatar is basically shorthand for his preference for doing things by consensus), and from the beginning ATT hammered out firm rules to prevent another Fast Eddie from happening. Geth also has tried to keep his personal dramas away from ATT, Atlantid's bullshit and Nate Spidgewood's madness notwithstanding for example.
Fast Eddie hated Geth from day one, and until Drew Schoentrup took over TV Tropes, Geth was basically banished from TV Tropes, and while there were some issues at first, Brent met Drew IRL to break the ice and over time TV Tropes and All The Tropes have formed a gentleman's agreement to keep the peace between them.
If you check Geth's early blog entries on Blogspot, he was pretty bitter and salty over TV Tropes, but he chilled out as time went by and even formally apologized for a lot of his rage (except for the stuff on Fast Eddie, he still considers the man his anti-role model), burying the hatchet around the time Drew took over, and as indicated by Geth when he told Nate to fuck off on /cow/ or he'd call the FBI, he and TV Tropes are firm allies when it comes to dropping the hammer on Nate's crazy shit.