I don’t think BM intended to set the stage for a mountain lion attack, rather, I think he took advantage of it. Here’s why:
The whole bike ride narrative, along with the bike being found, was done in an effort to stage an abduction.
The expectation is that they would see the bike, and then begin investigating an abduction. God knows that scenario has occurred before.
For whatever reason, the sheriff’s department, CBI, and FBI, didn’t bite. They seem to have known that she wasn’t abducted, and quickly began focusing on BM.
In response to this, or in response to speculation that an animal attack occurred, the “mountain lion” theory emerged.
Looking at that YouTube video, it appears that BM is pushing a mix of both. Basically, “I thought she was attacked by a mountain lion, now I’m not sure she was attacked by a mountain lion, but she still could have been attacked by a mountain lion. Also, maybe she was abducted.”
Muddy waters, yet not really.