How come before Jesus god needed blood sacrafices?

When im reading the ot its talking about blood sacrafices. Burning lambs, goats, bulls. There was one part were god says for your sins you must burn 7 bulls for 7 days straight and i think other animals in conjunction i think ot was in ezeikeil. How does sacraficing an animal into flames make god any happier about anything how does that earn his blezsing? Feel like people just adopted it from pagan practices because paganism was basicly everything before abrahamic religion and monotheism from my understanding.