Why would a guy suddenly start being really nice to a girl? ?

He rejected me over 1 year ago over having a gf I did not know about, he treated me so so badly after that and there were a load of complications where I played a few games also and eventually he blocked me and pursued another girl right in front of me. Now I’ve had a massive glow up and he hasn’t seen me in 4 months, we’ve been speaking on the phone a lot (for working purposes) and he is being extremely sweet & shy, speaking softly to me and being overly polite, calling me my pet name as well. He’s treating me better than before al the drama happened with us. Opinions?