It seems they are trying to get https working properly.
I wonder why they didn't let anyone know they were changing domains?
I bet they got a new server / upgraded because the old server was slow even for http requests. If they had gone with https on the old server... well... there would be no tomorrow...
1) They still could have let everyone know that they were changing domains. Forums were loading fine prior to moving.
2) They can point sub-domains to a different IP. So, changing to a domain (even though it's not a bad idea) wouldn't be required to change servers.