Why is it so easy for Meursault to accept his environment?

Basically the protagonist, Meursault, just doesn't care. Meursault is an existentialist thinker who has little ambition in life. He sees life as a series of events that have little reward or consequence. He handles his mother's death with a detached ambivalence. He holds this same detachment for all his relationships: he thinks that life unravels regardless of what we do or do not do.