First, believe it or not, 3 years is not that long. It's also not a given that LeCun was given the resources he needed to work on this tech at Meta. Zuck wanted another llama.

Second, AMI Labs just secured a billion in funding, and while that's a lot of money, it's literally just a fraction of the yearly salary they are paying to Wang. Big tech companies are literally throwing tens of billions to keep doing the same thing, just on a bigger scale. Why not try something else once in a while?