Officials did everything they could to prevent Palace from scoring the equaliser against United after the “pressure release” Casemiro red card.
Give a prominent decision against United after weeks of mounting scrutiny arising from numerous questionable (non)decisions over many games so as to make it seem like United aren’t getting favourable treatment but make sure it doesn’t actually impact the match result. And now they can continue the favourable officiating and just shout “but the Casemiro red!” every time someone highlights another suspect (non)decision.
This is how you do it for those asking how manipulation works via officiating.