Yes and no, let me explain, both Campo Santo and Valve have been pretty active on social media (Twitter in my case) as workers have always been talking with people, getting feedback, doing their stuff, etc... Campo Santo might have helped them to comprehend why a good PR movement is necessary, however, why starting using the Valve account now and not when it was created back in June? Half-Life reveal, that's the moment when they started using the Valve account seriously, not only that but they also connected all their accounts at once (Steam, SteamVR, Underlords, CS:GO...) and HL:Alyx represents a new era for the company.Just had a thought, that maybe valve's new found outwardness is thanks to Campo santo? They were always good at stuff like that.
Valve¡s account will probably be used for big things (new games, new hardware, BIG steam changes...) while their satellite accounts will still be used for their main purpose, each one for what they were created.
I don't really think Campo Santo was the reason for this but most likely another push in the right direction.