Even if Google did do that (which they’ve shown no signs of, and they are still far from a browser monopoly when you look at iPhone etc) it wouldn’t stop HTML from being read. Translating from HTML -> GoogleHTML wouldn’t be meaningfully different to translating it from Markdown.
It could be argued that AMP was that attempt, and the only reason AMP gained tractions was Google started using it in the carousel of their SERPs.
While Safari, when mobile is included, has ~17% of the market, that's not enough when you combine Google's browser share along with their search engine share.
