Gaming GPUs enabled it. That's random serendipidous connective tissue that was presaged by none of the people who wrote the first papers fifty years ago.

Individual researchers and engineers are pushing forward the field bit by bit, testing and trying, until the right conditions and circumstances emerge to make it obvious. Connections across fields and industries enable it.

Now that the salient has emerged, everyone wants to control it.

Capital battles it out for the chance to monopolize it.

There's a chance that the winner(s) become much bigger than the tech giants of today. Everyone covets owning that.

The battle to become the first multi-trillionaire is why so much money is being spent.