A simple thought. The rating progression for a heavily promoted, highly watched film like Hacksaw Ridge is completely different than for a shadow boxer like Moonlight. In the first case the majority of the audience — a huge audience — really wanted to like the film from the start, and it hit all the standard targets — heroism, patriotism, tear jerking. When the Oscar nominations came out, people who weren’t that excited about it decided to see it anyway, and may have dinged it a bit, but basically by that time nearly everyone who wanted to see the film had seen it already — the pre-oscar rating was a comparatively complete one.
OTOH, Moonlight had nowhere near the number of rooting fans. So the rooting fans and more discerning film buffs saw it and gave it rave reviews, and then when it made the Oscar spotlight, the mainstream audience — in this case a large less-enthusiastic group — suddenly noticed it, viewed it and hated it. Here, the pre-oscar rating was not at all complete.
Is it depressing, disgusting and exasperating that mainstream ‘Murka has such a hostile and mysanthropic view of humans different from themselves and such a love affair with heroic heterosexual men in over-the-top adrenaline fueled simple mindedness, and this never seems to change much? Of course it is. Is it a surprise that when the Murkans finally rushed en masse to see Moonlight they hated it and created a rating nose dive? No.