Your scenario is the type of scenario that makes sense. Why wait to DECLAS? Presumably because they don't want to give Dems a chance to cook up another distraction.
So probably the DECLAS contains some juicy details that prove neither Biden nor Harris are "qualified" to be President.
I would really like to know what kind of disqualification will be relevant here!
As for whether acting Pres is Pompeo or someone else doesn't matter so long as the Acting Pres hates the swamp and will resist it and tell all Americans to resist the swamp.