It’d be nice if they rewrote Safari on Chromium. I think we’d all be better to pool our collective resources to work on a single browser vs. a whole bunch of competing standards and implementations
The computing world would be better off if governance of Blink/V8/etc were handed over to a neutral third party. Similar to Linux. Chrome, Edge, Safari, Firefox, Brave, etc can all still exist and differentiate on the implementation, just like how Amazon Linux differentiates with Ubuntu.
You really don't want a monoculture of a single browser engine pushing badly designed and often poorly implemented "standards".
w3c (and whatwg?) have a rule of "two independent implementations before a thing can become a standard" for a reason.