Keep in mind that while everyone always thinks that Apple does things to be an asshole or 'special' or whatever, it's far more likely that it was just coincidence or bad timing. Apply hanlon's razor and the wold is a whole lot less shitty.
Regarding HLS vs. the rest: HLS was developed around 2008 and published somewhere in 2009 IIRC, while MSE was at least 5 years later. At the same time; MSE has been supported since Safari 8 (macOS) Around 2015, according to WikiPedia, which is the same year FireFox gained support for it. Not sure about iOS.
Practically: Apple supports MSE and some DRM natively on the desktop just fine, and YouTube, Netflix etc. are using it at least since 2015 or thereabout. Also, most embedded video players in HTML5 just load a simple player framework that switches to the best available option. That might be MSE or HLS, but in the past it would also switch to Flash, RTSP and that windows media stuff.
Regarding HLS vs. the rest: HLS was developed around 2008 and published somewhere in 2009 IIRC, while MSE was at least 5 years later. At the same time; MSE has been supported since Safari 8 (macOS) Around 2015, according to WikiPedia, which is the same year FireFox gained support for it. Not sure about iOS.
Practically: Apple supports MSE and some DRM natively on the desktop just fine, and YouTube, Netflix etc. are using it at least since 2015 or thereabout. Also, most embedded video players in HTML5 just load a simple player framework that switches to the best available option. That might be MSE or HLS, but in the past it would also switch to Flash, RTSP and that windows media stuff.