I can’t claim to speak for anyone else’s motives, but my understanding is Max Leograndis, who you are referencing, approached USPSA leadership repeatedly with proposals to make USPSA multi gun a) HF based and b) appealing to the splintered multi gun competitive pool. The leadership response was, “if you don’t like it start your own,” and so eventually he did.
Other than defending his title here and at a couple other key matches, it looks like his USPSA participation has been at a minimum for a couple of years. In that he’s not unlike the reigning revolver national champion, who shoots 1-2 matches a year, at most.
Or several former national champions who shoot weekly outlaw matches but 2-3 sanctioned matches a year.
I agree it’s a problem. I disagree that it’s highly accomplished shooters who are to blame.