[jmeister]

There was no gate-keeping. Yann LeCun was doing neural networks in the late 80s.

[visarga]

Late 80s was the second AI winter, it wasn't all peaches. Why do you think just a handful of people were working on neural nets?

[YeGoblynQueenne]

Because before backpropagation (mid-80's) nobody could train multi-layer neural nets.

Although to be fair, there wasn't "just a handful of people". Just look at Geoff Hinton's citations count throughout the '80s.