Can someone explain why it is also down when trying to access it via Tor using its onion address: http://facebookwkhpilnemxj7asaniu7vnjjbiltxjqhye3mhbshg7kx5t...

Or when trying ips directly: https://www.lifewire.com/what-is-the-ip-address-of-facebook-...

I would have expected a DNS issue to not affect either of these.

I can understand the onionsite being down if facebook implemented it the way a thirdparty would (a proxy server accessing facebook.com) instead of actually having it integrated into its infrastructure as a first class citizen.