With presumably a huge lead-in from the Saints-Vikings NFL game, WWE Smackdown on Fox last night was viewed by 3.3 million viewers on average throughout the program. That's Smackdown's largest audience since the debut on Fox in Oct 2019 did 3.9 million.
http://www.showbuzzdaily.com/articles/the-sked-friday-network-scorecard-12-25-2020.html

The hour 1 average to hour 2 average went from 4,097,000 to 2,574,000, a decline of 47%.

Jumping to conclusions is tempting, but it's hard to say what that means without more granular data.

Was the Smackdown audience down to its normal number by the end of the program? We don't know from this data. If so, that would mean essentially none of the NFL viewers who aren't regular SD viewers stayed to sample.

Hard to say what this will mean even next week when they run on New Years Day, as the holiday may negatively impact viewership.

Based on past years' trends, January should be month-to-month growth period for WWE viewership.