Big Mike and the Gang is hardly a ratings juggernaut.
The live-feed numbers showed around 1/2 of their first night numbers in 2016. There's more data to be gathered but it would be a miracle for them to get into 2016's ballpark.
Apparently viewers are more interested in watching some reruns than watching the DNC broadcast.
https://www.hollywoodreporter.com/live-feed/tv-ratings-monday-aug-17-2020
https://deadline.com/2020/08/nbc-abc-monday-tv-ratings-2020-democratic-national-convention-1203016422/