I think the idea is that so far, and for now, the chargers have indeed helped them keep a significant lead in EV sales. Eventually though, many other companies

I think the idea is that so far, and for now, the chargers have indeed helped them keep a significant lead in EV sales. Eventually though, many other companies will also be selling very good EVs, and if Tesla doesn't open their chargers, the rest of the industry will standardize on something else, and it will eventually get good (or at least good enough) out of necessity. So instead of being the only decent option, Teslas will be the odd one out that have their own weird charging setup. As long as that setup is good it might not be too much of a detriment for them, but eventually it would stop being a major benefit either. So, better to use their current position to become the dominant charging solution for all brands. They were never going to corner the EV market long term. But they actually do have a chance of being the dominant charging supplier for every car on the road.