Shedding half a pound in an hour when you're already completely drained isn't exactly easy, whereas it probably wouldn't have been an issue if he had seen he was still over the night before.
Gaethje, Rose, and Carla all came in at the title limit. Fighters frequently cut to half a pound or so below it when they're fighting for the belt, so it's not inconceivable that those three did and the scale issue balanced the numbers out to exactly the limit, to which they just shrugged their shoulders.
At the end of the day, Charles had never missed weight at LW before this incident. Weight bullies are either 4-6 inches taller than the divisional average and/or have problems making weight even with the 1 pound allowance, which Oliveira obviously didn't have last week. Also, they'd have no chance in hell at cutting to a lower division in the past. Using the weight bully excuse because the fighter you were rooting for lost after one very questionable half pound miss is kind of pathetic.