He was never traumatized. It's a combination of faking it, and convincing himself it's true.
If you go back to the London thing, the day after the convention he went on a trip to Scotland with his then girlfriend and blogged about it, and then he wrote an infamous blog post in which he compares the peculiarities of British food courts with the American ones, and he also participated in a podcast with Humon. When he came back home, he drew a bunch of SYAC comics about his experiences in the convention... In summary: he took the incident like any normal person would, and continued his normal life. There was nothing to indicate his life had been ruined by a horrifying traumatic experience, or that he was reduced to a sobbing mess in a corner of his hotel room.
And this was before the Brentalfloss era, which he has admitted has been the most productive and most lucrative time in his life. So the incident didn't destroy his life, as he claims now. He was perfectly able to work and be productive afterwards.
This bullshit started years later, maybe in 2015 when he compared his "London attack" with the Charlie Hebdo terrorist massacre. This got him some free asspats, and that made him realize that he could exploit the incident for pity and excuses. Furthermore, he had become an SJW by then, and he figured you can claim oppression points from PTSD (a conveniently invisible and impossible to disprove mental illness).
Since then it seems he has been making the "attack" worse and worse in his mind, probably convincing himself that it really was horrible. And whenever he brings it again, he gets more asspats and more excuses to be lazy, which creates a feedback loop to make his "PTSD" even worse, and so on.
At this point, from the way Dobson talks about his "illness" online, and how he needs so much "healing and recovery", it seems his made up trauma has taken over his life completely. I can imagine his home life must be something like this:
"Andy, come to dinner, the broccoli is ready!"
"Hmff... nnngg... I want Big Mac..."
"What?"
"........................................................................ I want Big Mac!"
"Honey, we talked about this. You have to eat vegetables too..."
"BUT MOOOOM!!! YOU DON'T UNDERSTAND HOW IT IS LIVING WITH THIS HORRIBLE TRAUMA!!! I NEED COMFORTING FOODS TO HELP ME HEAL AND RECOVER!!! IF YOU FORCE ME TO EAT THINGS MY BODY IS NOT READY FOR, YOU'RE HURTING ME EVEN MORE!!! WHY DO YOU WANT TO SABOTAGE MY HEALING AND STOP ME FROM GETTING BETTER???"
"Oh for fuck's... whatever... I'll call Uber Eats..."
"Humff... And I want Mario Odyssey..."
"What???"
"I want Mario!!!"
"Sweety, we decided that it was better to wait for your birthday before we buy you more games, didn't we? And you promised you'd do your chores if we bought you the Sky Rims, but then..."
"OH MY GOOOOOD MOOOOOOOOOOOOOOOM!!! HOW CAN I DO CHORES IF I'M IN CONSTANT UNBEARABLE PAIN FROM THIS HORRIBLE DISEASE??? I'M A SICK PERSON THAT NEEDS HEALING AND RECOVERY TO LITERALLY NOT DIE, AND INSTEAD OF TAKING CARE OF ME, YOU WANT TO FORCE ME TO WORK TO DEATH!!! HOW CAN YOU HAVE SO LITTLE EMPATHY FOR MY UNIMAGINABLE SUFFERING??‽!! - BESIDES, I SHOWED YOU IN THAT WEBMD PAGE: PLAYING VIDEOGAMES IS PART OF THE TREATMENT!!! I CAN'T BELIEVE YOU REFUSE TO GIVE ME THE TREATMENT I LITERALLY NEED TO SURVIVE THIS ILLNESS!!! THIS IS CHILD ABUSE!!!"
"*Sigh*... Whatever... I'll buy you your fucking game... And you're 37 by the way..."
"Huff... puff... and pre-order Yoshi."
"..."
