They recently refunded every purchase made on stadia when they announced it was going to close down, and they created 2 first party studios for it (along with deals with rockstar games etc.)
Did stadia itself make any money? Probably not. I'm sure the money they made from re-using those servers for their cloud/ai departments certainly paid of the dept though.
But derefr's explanation is the other way around. Google built the servers for the cloud/ai department and crated Stadia to reuse them. To me it seems that it couldn't have been profitable even if we say Stadia got the servers for free.
afaik stadia used custom built hardware from amd's instinct line. Almost all of their cloud offerings are nvidia based or utilize their own TPU's.
I can't say for certain that derefr's explanation is wrong, but from what it looks like they did create bespoke hardware for stadia instead of reusing their existing infrastructure.
Did stadia itself make any money? Probably not. I'm sure the money they made from re-using those servers for their cloud/ai departments certainly paid of the dept though.