Three possible reasons why Joe went to Camp David.
1. They have been stonewalling questions about who was visiting Joe in Delaware. They can cover up visits, say from medical specialists much more easily at Camp David.
2. Especially if they need high level military and State Department officials there, the meetings are easier to do and, again, easier to conceal at Camp David and the comms for the bigshots are much better there.
3. Finally, the fever swamp conspiracy theory. Joe is more easily protected there. Did they get intelligence that said the Taliban was threatening him? More feverishly, are they themselves planning a big false flag event where Joe will need protection from domestic terrorists?
Another possibility. Would they even announce anything, right now, if he was seriously ill or ….?