How can Trump invoke executive privilege over material already made public?
How can Trump invoke executive privilege over matters that happened prior to his inauguration?
How can Trump invoke executive privilege over matters that he was not an participant of after he became President?
And this idea maybe dumb but,
If he his invoking his executive privilege over all kinds of matters that tax payers don’t get hear about then the cost of said investigation should be deducted from his salary and/or all future salary until such time that the cost has been paid in full. There should be cost associated with privilege, and that privilege shouldn’t be cheap