I'm glad someone else in the comments posted this link: https://netsplit.de/networks/top10.php which clearly indicates freenode is tanking and libera is matching it but upwards. In a month it'll be overtaken; I think there may be a lot of inertia from people who have a load of irc channels open but don't actively interact with it, as well as old webpages pointing to the freenode servers. But it's a matter of time, nobody will promote freenode anymore, all IRC communities will or have migrated, etc.