Meta has a moat. That moat is the connected graph of users across its various properties, and the (monetisable) attention of those users. Making LLMs a commodity reduces the likelihood that OpenAI (or someone else) will build a unique, unreproduceable product that rivals Meta's properties for attention.
2) Free research and innovation that Meta can readily copy for their needs.
3) They don’t really give up any power. They can always keep future models proprietary.
In my opinion, it is a bit like Microsoft’s “Embrace, Extend, Extinguish.” Make SW publicly available, extend it to your own business needs, and if a competitor emerges, the power is still with Meta to restrict its use or copy the use case (“extinguish”).
From the outside, it seems LeCun is most interested in the science and progress of ML/AI and has convinced Zuckerberg that open is also good for business. I’m not sure if that’s true, but it might be.
The business model that consists in selling a subscription to be able to query a LLM isn't much of one: it's a race to the bottom. Users will switch as soon as anything even slightly better is out (like cancelling ChatGPT and taking a Claude 3 Opus subscription), companies with similarly performing models have to compete on price. It's ugly.
By making models freely available and by buying and advertizing that they bought a shitload of NVidia GPUs to train AI models (LLMs and others), Meta is adding additional pressure to those already fighting in an overcrowded market.
They don't do it because they'd suddenly be nice: Meta is still a despicable company with despicable tactics. It's all about screwing these one-trick ponies as much as they can: last thing Meta would want would be a tiny player to become a trillion behemoth.