why is there such a deep rivarly / hatred between moroccans and algerians?

hello! asking this as someone who comes from an algerian family, i've always wondered why my family talked badly about morrocans for no reason? for example, my mom is currently watching football and keeps repeating how badly she wants morocco to lose... my grandpa has always been judgemental about them, saying that they practiced black magic, which is also a thing in our culture? very confused.

i've had friends who came from morrocan families as a teen and they also told me that their parents talked this way about algerian. so, my question is, why and where does it come from? it all seems very silly to me considering how similar we seem from the outside. thanks.