How is it fair for big companies with a lot of money to take creators’ work, without (or minimal) paying/attributing them, while those companies then use these technologies to make more money?

Because those works were put online, at a publicly accessible location, and not behind a paywall or subscription. If literally anyone on the planet can see your work just by typing a URL into their browser, then you have essentially allowed them to learn from it. Also, it's not like there are copies of those works stored away in some database somewhere, they were merely looked at for a few seconds each while a bunch of numbers went up and down in a neural network. There is absolutely not enough data kept to reproduce the original work.

Besides, if OpenAI (or other companies in the same business) had to pay a million people for the rights to use their work to train an AI model, how much do you think they'd be able to pay? A few dollars? Why bother seeking that kind of compensation at all?