Of course the Hugo obviously shouldn't just be "#1 book [in genre] on Amazon" because the entire point of awards is to focus on quality, which may not always be clearly reflected by sales. But when even the relatively small minority of people buying the winning book don't seem to like it as much as other books, something is quite wrong. Let alone the fact that Project Hail Mary came in last place, also behind books like She Who Became the Sun. [2]
[1] - https://www.amazon.com/Desolation-Called-Peace-Teixcalaan-Bo...
[2] - https://www.amazon.com/She-Who-Became-Shelley-Parker-Chan-eb...
I like Project Hail Mary, too, and it's certainly more popular because the author is far more well known, but there's no question in my mind which one is "better", certainly in terms of deserving to win an award.
The vote also is not fair. People publicly organize voting cliques on e.g. Reddit (to say nothing of what's happening in private), and the new system is extremely exploitable. But I think that's beside the point. The issue is the outcome. The Hugos used to not only reliably reflect the best in genre works, but also select works that would often be talked about decades later. How they achieved that is irrelevant, only that they used to be able to do so, and now do not.
I think the groups that coopt, or try to coopt, these sort of things (which obviously also includes the Puppy stuff), fail to realize that the prestige of something is not based on that thing itself - but on the value of that which it promotes. If MIT just started enrolling 'merely above average' students and printing out diplomas, then they'd quickly lose their prestige. The same thing has happened here.