In February, xAI reorganized. Then its leaders left. 

As cofounders left, Elon reorganized xAI in February. Then, the leaders under that new organization also left.

We preserved the names used in Musk's February all-hands meeting notes as written. "Heiner" is a nickname for Heinrich Küttler and "Makro" refers to Manuel Kroiss, who both left. Guodong Zhang, Haotian Liu, and Lianmin Zheng have all left.
Source: Fast Company