Just wasted half an hour or so trying to find the problem. 
Apple.
Here’s a shell command to remove the /etc/hosts line:
sudo sed -e '/^0\.0\.0\.0 ocsp\.apple\.com$/d' -i '' /etc/hosts
I’ve tried that on Mojave. sed is a standard Unix command from long ago, so I highly doubt it’s changed in Catalina or Big Sur, but just as an FYI I haven’t tested it on either of those (or earlier than Mojave.)