https://www.pcgamer.com/shadow-of-the-tomb-raider-review-bombed-because-of-34-discount/

Andy called Shadow of the Tomb Raider "one of Lara Croft's best modern adventures" in his review last month and, up until this week, fans seemed to generally agree, giving it mostly positive reviews on Steam. But then it was review bombed, with most disgruntled fans citing a 34% week-long sale, which ends tomorrow, as the reason for criticism.

From reading some of the 600+ reviews since the sale went live (66% of those reviews are negative), the main line of reasoning is that it's unfair to have paid full price for the game, either as a pre-order or at launch, only to see it heavily discounted so soon after.