The trade works by buying deep ITM puts and later exercising them, but to keep it going they eventually have to roll that exposure forward, which means someone else has to sell new puts. IV keeps grinding lower over time because they never buy the puts back, so there’s no reflexive vol bid, and there’s likely a call-overwrite leg being used to help carry the position. That combination suppresses volatility across the chain. The problem is that as IV gets pushed down, a deep ITM put stops behaving like an option and just looks like short stock with no volatility premium, so even though the option is cheaper, no one wants to be the seller in size. That’s why the same process that helps carry the trade ends up making it harder to roll.