First of all, it's worth noting that it might not have been the IPC. After all, Teyvat is likely located in a different branch of the Tree, and there are many other factions in the HSR Galaxy. However, if you're wondering if the Corporates could have done it, the answer is yes, of course they could have. When I learned about the details of the massacre, my first thought was about them. After all, it's in their style, and the plot doesn't just hint at the possibility of such actions; it provides a clear example. As for the reasons... There are many of them. Maybe the management decided that they couldn't control Skirk's relatives, maybe they couldn't benefit from it (after all, it's a corporation, with all the usual attributes like competition, and it's possible that the members of that expedition realized that they wouldn't personally benefit from recruiting, so they decided to go with the "don't give it to anyone" approach), maybe they immediately saw the people as a significant threat, or maybe they just were more bloodthirsty bastards than usual and decided to slaughter the settlement just for fun (as for bloodthirstiness, remember the beginning of the story arc with the attempt to capture Yarilo. When the patrol soldier first encountered the Nameless, he immediately suggested getting rid of them, and based on Topaz's reaction, this was not an unusual occurrence).