Taught how to make friends. They need to be taught what questions to ask, how to ask them, how to respond, how to look at people, how pat nice, what not to do (don’t tattle, or be a sore loser, or a bad winner, or mope when people won’t do what you want, etc.)
They don’t automatically pick up these social skills. They don’t recognize the social queues others give off. So they have to be taught sometimes. Practice with him.
Heck there’s probably even some videos on YouTube on how to make friends in elementary schools.