He probably doesn't want anyone to know that he's broke and getting a huge payout from the Clintons.
That "payout" would end up being in government contract's worth $Billions. Donald ain't doing this for pennies, or mere $millions.
The fact that Trump is not raising at least half the money he needs for the Presidential campaign is evidence that there's no real support for him. Whoever is answering these polls in Trump's favor, is NOT sending Trump checks. That's very, very weird. Unusual, as in, unheard of. Sure, the big players raise the really big bucks, but Trump has STILL not raised what Cruz raised for the primary, and the vast majority of his support came in $10 and $25 amounts from his grassroots. Trump has nothing like that.
NO MONEY = NO SUPPORT
Trump is an island.
Second, if one posit's that Trump's ego would not allow his campaign to ultimately flounder due to lack of funds, as I do, you'd expect him to pony up significant funds, at least $250M up front, just to secure media ad slots before Hillary blocks him out of prime time slots. Then, another $250M a month until the GOP donors (either the big boys or regular voters) catch up.
The fact that he has not done so, AND refuses to release his tax returns, tells me he's likely heavily leveraged. He does not have the cash. His assets are heavily leveraged, as in "junk bond" status. He can't borrow against them. If he sold a major asset to raise the cash, it would not return sufficient cash to make a difference, again, because his "assets" are hollow.
My guess is that he's one interest rate tick upwards from losing a lot of his paper "net worth". Otherwise, he'd have pony'd up the cash by now, and he'd have placed his advertisement block orders. (He's also have staffed campaign headquarters in every state and territory.)
Trump is an island, broke, and totally out of his element in running an election. Something really bad is going to happen to disappoint Trump supporters, that's my guess.