They had paid for it for years.

Yes. With the intent of making a profit eventually. Or they wouldn't have.

They combat this with the price of add on devices, wall mounts, hdmi cables, etc.

What is YouTube going to "combat" with if not advertising or subscriptions...?

This is where my brain says fuck you. One billon means you’ve won. Stop being a greedy dick.

One billion means nothing if you're spending tens of billions per year to continue operating. I'm not suggesting the CEO of YouTube deserves to get richer. I'm saying the company has operational expenses and investments that require some level of profitability, and "free for everyone forever" is literally just not a viable option.