My guess is, that Solution 9 is a digital repository of consciousness from people trying to escape the final days or one of the calamities. In a digital world there is no need for things like work and survival and therefore entertainment would be king. The Arcadion seems to me to be a play on the word Arcade. The clue of it looking like a big GPU is that it could be a big game. Maybe over the course of time the consciousness's inside have needed more and more extreme versions of entertainment and The Arcadion is their version of a coliseum.