I'd say it's more of a testament to the flat structure that Valve has used as its management and development strategy being able to withstand incursion. Unfortunately, the extra wokeness that got brought along with Campo Santo pushed it over the edge, as the cult of SocJus had previously started to infect the whole place. We saw it creeping in with Valve's Greenlight and other small-creator programs, and much like cancer, unless you catch it early it'll spread and take over the whole place.

As for "Why Campo Santo?", that's a question that's up for debate. I recall a few articles saying something along the lines of Valve buying up studios because the studio had some skills or tech they wanted (like the AI in Led 4 Dead), but Campo wasn't exactly reinventing the wheel with Firewatch. At best, they pulled off a boondoggle by getting the wokenistas to all circle-jerk over their walking simulator, so maybe some SJW that had gotten their foot in the door decided that Valve needed a new Storytelling unit or some similar bullshit. Either way, the only thing they've done since they got there is work on Half Life: Alyx and produce a few stills for another walking sim they're supposedly working on.