The URL Standard didn’t even consider contacting any industrial vendor that relies on them - e.g. SIEMENS. There’s entire industries out there that use these standards, and rely on them to be stable.
The only participants were all either browsers, affiliated with browsers, or a handful of web serving projects.
Other projects that rely on URLs include everything from KDE to Gnome, Microsoft’s OS to the systems used in your car.
Changing a URL standard and only involving web vendors is basically like changing the A4 paper standard and only talking to the Microsoft Office team, the Google Docs team, and HP’s printer team – while entirely ignoring paper manufacturers, envelope manufacturers, the mail companies around the world that will have to ship the envelopes, fax manufacturers that have to build faxes able to fax the new format, newspapers and magazines that have to replace their paper, newspaper shelf manufacturers that build newspaper shelves for newspaper stores, etc.
Most of the time, it’s easy to only think of the web as browsers and servers, but some of the specs the WHATWG touches go through entire industries, sometimes there are millions of companies that have to be notified months or years beforehand to replace their software, update it, potentially even do a recall, and standardize. Not everything moves as fast as the web.
And this entirely disregards the people that are trying to parse the web with HTML parsing, which everyone loves to ignore. And so many other groups of people and companies.