LeCun wasn't producing results. He was obstinate and insistent on his own theories and ideas which weren't, and possibly aren't, going anywhere. He refused to engage with LLMs and compete in the market that exists, and spent all his effort and energy on unproven ideas and research, which split the company's mission and competitiveness. They lost their place as one of the top 4 AI companies, and are now a full generation behind, in part due to the split efforts and lack of enthusiastic participation by all the Meta AI team. If you look at the chaos and churn at the highest levels across the industry, there's not a lot of room for mission creep by leadership, and LeCun thoroughly demonstrated he wasn't suited for the mission desired by Meta.
I think he's lucky he got out with his reputation relatively intact.
I think he's lucky he got out with his reputation relatively intact.