I thought the same thing but maybe it is better to trickle this out slowly. It gives Biden more time to deny. He already is backing off on having met with the Burisma guy. At first it was not on his official calendar. Now it’s maybe they met.
If they can illicit a denial from Biden's campaign - knowing they have the goods to blast any denial into the stratosphere - then a slow drip might be a good plan until the final dump.