This is the appeal to authority fallacy. Just because the "smart guys" say it, doesn't mean it's true.

Bill Gates, Elon Musk, and especially Steven Hawkings, are the most overrated "smart guys" people regularly reference as truth bearers. Neither of the three are experts on artificial intelligence, they're simply versed in it. The actual experts on A.I. have varied disagreements with these doomsday scenarios.

To be clear, they're not exactly saying "It's gonna happen", they're just accepting the potential dangers of it which is very different than outright saying it will end humanity. What bothers me, is that everyone talks about how they warn about the potential dangers but forget to mention that they also say it could be a great thing, too.

Here is the perspective of actual experts on the matter.

https://futurism.com/ai-researchers-disagree-with-elon-musks-warnings-about-artificial-intelligence/

Judging from history, we will converge with these new developments. Just as we once were unconnected without the internet but are now connected worldwide and communicate with one another, we will slowly become integrated with the systems of artificial intelligence. That's what IoT, Big Data, the blockchain, and A.I. are leading to, not a separated entity that will destroy humanity but rather, something that will transform humanity into something even greater that's capable of unimaginable things.

The real problem is that people have a naive perspective on what life is, what humanity is. We perceive ourselves as separate from that which we create and evolved from but in reality, we came from the stars and are simply evolving in order to return to the stars. The cosmos created a way to see its own reflection, evolving into its own introspection. Being afraid of A.I. "ending" humanity is like being afraid of the basic compounds of life crashing into Earth in order to create the lifeforms that inevitable lead to us, which lead to A.I.