Because Greer Love brainwashed his brother with dreams and material possessions. His brother was going to school to become a sports agent, he wanted to represent Mo and hopefully other athletes he didn't just wanna leach off his brothers success. He told his brother he wanted to go to Texas for grad school with him, initially Mo thought it was all a great idea. However, Greer Love already had agents and people he wanted to hook him up with. His brother also wanted medical care from Texas for their mother, Texas has a renowned medical program, she is elderly. Mo started changing not answering texts, he told his brother to not come to Texas with him, and he told him to go back to the block (112th and Lenox in Harlem) for a year until he was drafted I guess. His brother doesn't like how his brother is changing and all the shady shyt behind the scenes, as well as how he's treating the family. That's why he's doing all of this.