Namely : Sam Altman, Microsoft and self-fulfilling prophecies.
1. Sam Altman - OpenAI does relationships like no other company. They are getting doors opened to data that others (even big companies) simply do not have access to. having Altman at the helm has a lot to do with it. He is also the reason OpenAI is arguably second only to Tesla in terms of being a self-marketing behemoth with no real marketing budget. The super-fans do all the talking for you.
2. Microsoft - Whatever the fine-print of their relationship is, despite not owning OpenAI, Microsoft is throwing its entire weight behind them. This means that the entities who can compete on compute and endless money supply are Google and Amazon. The fact that Microsoft obscures its relationship with OpenAI, also means that OpenAI gets to move with the sort of agility and goodwill, that something branded MSFT/AMZN/GOOG simply cannot.
3. Self-fulfilling prophecies - These models get better with human in the loop (HITL) feedback. OpenAI is the one getting the most human in the loop feedback due to being first movers and that lets them make better models. The better models mean that users keep coming back to OpenAI to give more HITL feedback.
(This is more so true with NLP than Vision. Vision has a healthy set of competitors across the board)