Destroying the open web? What are you talking about? Apple has a fantastic track record of making Safari a world class web browser for iOS. If Microsoft, Google, and others made these gaming offerings web apps, they’d likely work just fine.
From a quick glance it looks behind Firefox and Chrome on HTML/CSS/JS feature support.
https://caniuse.com/?compare=firefox+84,chrome+89,safari+14&...
And then there's Safari's broken autocomplete:
The reason non-WebM stream services might work on Safari is because said service engineers implemented alternatives to it.
There is wisdom sometimes in saying "no."
There's also no wisdom in Safari preventing users from viewing a widespread royalty free media format. It simply causes frustration which is evidenced by the many frustrated customers in results for "safari stream not working "webm"" search.
There's of course a balance to be maintained; if we single-source our streaming video codecs, that will dampen innovation in that space. But I'd hope there's a less wasteful middle ground than the place we're at now.
Technology license cost is not the only consideration that goes into business decisions. Consider the whole end to end process of making, distributing and consuming video, and all the parties and technology providers involved, not to mention installed bases, cost of switching, etc.