I think it’s a strategy.
No press conferences. They’re risky.
She’s terrible at rallies. Shrill, and boring all at the same time. Small crowds create bad optics to boot.
She does lose support the more people see and hear her. Better to let surrogates make up BS.
And there likely is some truth that she is not well. She certainly lacks stamina.
I agree that her numbers drop the more we see of her, but scripted events are pretty safe and keep your campaign in the news. She is a ghost. This is prime time for the election unless she is planning for a burst after labor day, but even then it is still very unusual.