Another thing they apparently do is let business owners (e.g. hotels) remove negative reviews because they're "defamatory".

I had a very factual 3-star review on a hotel that was supposedly very quiet, but was super noisy and the AC was not working. And there was literally nobody at the reception at the time of check-out and nobody picked up the phone either. All in all, nothing serious, but worth a review. Purely factual stuff, nothing bad-mouthed, just my experience and three stars.

A few months later the review was removed because it was "defamatory". I was able to get it reinstated by sending them proof of payment to the hotel and proof that I was there. A few months later, it was removed again! That same dance was repeated six times..... What a weird system.

I'm surprised you knew it was removed. All my negative reviews appear visible to me when logged in and disappear when logged out.

Only sure fire way I've found is to leave a two star review with no body. One star without a body is also shadowbanned for me.

Yet another example of how the incentives work when the platform makes its money with ad revenue. The hotel pays Google for ads and gets favorable search results. If Google then hosts a negative review, the hotel might be less inclined to advertise there. So, only positive reviews get published.

The reviewer isn't contributing to Google's revenue at all, so his honest review is only worth something if it makes the advertisers happy.