Of course they knew. The plan was to run Donald out, make Cruz the nominee, then release this in early October and destroy him.
That was the plan all along, and why the GOPe has been
totally comfortable supporting Cruz as their tool to force a Contested Convention. They had two reasons - (1) Cruz was the only person who could, at whatever level, compete against Trump and (2) at a Contested Convention, they could then release detailed information on the (alleged) affairs and use that to take Cruz out of the running. Consequently, they could then put a third person that is neither Trump nor Cruz.
In a nutshell, this is why the GOPe were totally comfortable supporting Cruz. They had a poison pill prepared.