There was a good API before Elon essentially shut it down. But that is irrelevant.
The reason mass data scraping like OpenAI does would not rely on an API is because they are getting data from the entire Internet (and other sources that aren’t online). They want raw data and they want as much and as varied as possible. It’s much easier, cheaper and practical to build tools that scrape websites generically than to integrate with thousands of completely independent and different APIs.
It’s the same reason that Reddit complaining about “AI taking all of our data” is bullshit. “AI” is just a convenient excuse and the most recent tech buzzword.