John Cena has been getting booed most of his career in WWE, he was still the biggest draw and merchandise seller, then it was Roman Reigns (until he got cancer), they booed Charlotte Flair (Ric Flair's daughter) because they liked someone else better, the same with Ronda, especially at these big events that seem to bring in the more hardcore fanbase, they seem to go against someone they think is being pushed above someone from the independent scene, basically they hate you more if they think Vince McMahon is pushing you above who they want to see as the hero.
Brock Lesner barely shows up and let's Paul Heyman do his talking, so it doesn't bother him if they cheer or boo him, he gets paid either way.