At the end of episode 11, it looked like CT was going to volunteer to compete against Devin in The Crater. He wanted Josh, but the house voted in Devin.
Then, Lolo left. There were too many guys in the game and there was a “security breach.” Suddenly, we saw our first double elimination of the season. This gave CT full power to take on Josh if he wanted. And he did.

Some people will argue that this was simply a response to Lolo’s departure. Lolo might argue otherwise. She’s openly stated production told her to leave. Then, Josh and Nany had to go down into The Crater because they got the second most votes.
So was this rigged? I’m going to go with kind of.
I don’t think Lolo’s departure was rigged to set up a CT vs. Josh elimination. But I do think production saw the opening and they wanted to give CT what he wanted. This season has been plagued by six non-elimination departures. They need to do something to make the game interesting.
Josh has even said his harness was loose during the elimination. Production did nothing and just let CT finish the puzzle, though Josh said that CT was ahead and killed the puzzle.

All of the evidence looks fishy. But, we also need to look at the scenario without Lolo leaving and the security breach. We would have seen Devin vs. CT in elimination. If production wanted to rig things, just send down CT vs. Devin in a headbanger. Suggesting this whole incident was rigged would overcomplicate things.
If production did anything, they tried to flush the weaker competitors out of the game to stage heavyweight eliminations in the next couple of episodes.