I'm just guessing but it looks like a Rube Goldberg fix by a former owner, probably to suspend items from the top while leaving the floor clear?
I am assuming you bought the TT used? Doesn't look like anything factory installed (job is much too neat for the Jayco assembly line
)
I have all sorts of little hacks on my trailer. If I ever sell it the next owner will probably go nuts figuring it all out!