... suretors refused to accept Trump’s real estate as collateral. Instead, they would only accept cash to the tune of $1 billion, which Trump said he and his businesses just don’t have.
If they want cash as collateral, that cash would go into an escrow. Why would you tie up $1B in escrow in order to get $500M? You wouldn't; you would just use the cash you had.
It's like going to a pawn shop and asking how much they'll give you for a $20 bill, and they say $10.