Why did they put it in writing?

I come back to that question every time something new pops up on the wires about Dominion Voting Systems’ defamation lawsuit against Fox News. Endless commentary (mine included) has dwelled on the audacity of Fox hosts and managers in credulously airing allegations they believed to be false about a matter as grave as the integrity of a presidential election.

But the most audacious part, which is less often noted, is that they expressed their doubts in written communications to each other. 

They must have known those communications would be discoverable if they were sued. If they didn’t, in-house counsel at Fox would have clued them in. To all appearances, they never thought to ask. Why?