I'm pretty sure Ian Hickson is no longer involved with the WHATWG. I think he's working on Flutter now (
https://news.ycombinator.com/threads?id=Hixie).
In fact, I would say that it's not quite like a cathedral and bazaar here.
The W3C is like a legislative committee. Lots of things done by committee vote. Formal process that must be gone through to advance beyond committee. Petty politics that screw with actually getting things done. The committee chair having the ability to block work by procedural means.
The WHATWG is more like an open forum. The work happens out in the open. Anyone can participate in the discussion (the W3C committees frequently have private meetings, there have been private mailing lists, and so on). There are a few people who have commit rights to the repo, so who actually control what goes in and what doesn't, but they are generally willing to let in changes that have broad support, and are implementable, rather than letting such features get held up by political processes.
Besides the difference in structure, there's just a difference in attitudes. The W3C tends to strongly favor certain principles, like accessibility and modularity, but to the exclusion of compromise for technical reasons or real-world reasons. They also seem to have a tendency to get very attached to particular ways of doing things, without being willing to compromise. I think the biggest example of this was longdesc; it was never implemented properly in pretty much any browser, and very few people actually followed the spec and had it point to a URL (many people just copied the alt tag, or provided a longer description in the attribute instead of a URL), so even if browsers or screen readers had implemented it, the content wouldn't be useful. But people in the W3C made a big stink about removing this, and spent a lot of time and effort fighting and litigating over that, rather than actually trying to work on a different feature that could gain wider adoption.
The WHATWG tends to take a more pragmatic approach; pave the cowpaths, if there are differences between implementations do it in the most sensible way that preserved compatibility.
Now, what the WHATWG has produced hasn't always been the best; there are times when it's made mistakes in its approach. The drag and drop spec, which had been reverse-engineered from IE's drag and drop support, was a pretty bad; not sure if it's gotten better since.
But overall, the WHATWG has been a lot more productive in getting standards done that are actually used on the web, because they involve the implementers, and don't override them with tedious, drawn out, political battles over obscure features that no one uses.