I highly recommend Whitaker's "The New Quantum Age" https://global.oup.com/academic/product/the-new-quantum-age-... for (what I think is) the fascinating history of Bell's Theorem and the subsequent experimental work.

When Bell published his Theorem, work on the fundamentals of quantum mechanics was pretty much universally discouraged, and certainly out of the main stream. But it turns out, Bell himself said (according to Whitaker's book) that the reason he published in this obscure journal was due to page charges - he was a visitor at Stanford and didn't want to ask the host institution to pay for it, since it was a side-quest for him. Surprised the linked article doesn't mention this.

Bell proved that the universe is weirdly connected and that local hidden variables do not exist.