My ex still texts my mom and he’s engaged?

Background: my ex lived at my house for about 6 months, while I was in college (lived w my parents and brother). however i decided to end things. before he left he decided to tell my father that i said “i hated him” and i “hated” coming home and didn’t like any of them… which i never said. the only thing i said was i don’t like the negativity at home when i do go home because it’s always like i’m doing something wrong or not good enough. fast forward. i break up with him, a month later he’s with someone new and i’m talking to someone. he thanked me for ending us. now continuing on (i found out what he told my family and LOST all respect. my sister hates him etc.) now he still texts my mom. he texts her how he got a new vehicle, asking how she is doing and the family is doing etc. on facebook messenger. However he unfollowed every single one of my family members and blocked me on social (i originally unadded him). back when i ended things he told me he’d hang out w girls behind my back and got a porn addiction again. but anyways, fast forwarding it to now. I told my mother i’m not okay with him texting her or her texting him. she first tried telling me that she is waiting to ask him how i am doing… however yesterday he got ENGAGED. and did not tell my mother that. i found out from a close friend because she showed me a photo. i still continued to tell her that i’m not okay w it and tried to justify it by saying that she follows ex’s on social media… however my ex messaged her after she posted my boyfriend and i asked if she was mad at him? and he wasn't following her facebook anymore… Overall, the advice i’m looking for or clarity i guess is WHY is my ex texting my mom. why is she okay w it when HE smeared MY FATHERS NAME. Does this make sense to anyone?
My ex still texts my mom and he’s engaged?
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