At some point the official cosmology of D&D outright copied the beast lords and elemental lords from Moorcock. Although unrelated, D&D also devised a bunch of beastfolk races over the years.

To my knowledge, the two have never been linked in official materials or even 3pp.

I always thought linking the two could answer a lot if cosmological questions as well as provide some meta-commentary on taxonomy.

In real life, cats, dogs and hyenas are equally distinct. In fantasyland, is there a beast lord of hyenas or do the feline and canine lords compete for ownership? Is there an entire peerage system for the different taxonomic subgroups, like an Underlord of Foxes or a Baron of Maned Wolves? Where do fictional creatures like gryphons, manticores, hellhounds, sabertooth mouse lions and banthers get patronized? What even qualifies as a "beast" for this purpose?

There's been loads of different ways to represent beastfolk presented in D&D and 3pp. Typically beastfolk are just ad hoc, like catfolk and dogfolk and so forth. In some books they're presented in some more universal manner, like catfolk having a caste system for different pantherine genuses (and similar schemes for other types, like cervinefolk covering deer, elk and moose), or bloodlines based on mammal or reptile rather than genus (to cut down on the number of distinct races), or (my personal favorite) humans with animal heads.

I don't remember seeing the idea in any book, but something I came up with was that beastfolk were actually converts to the beast lord religion and gained animal features by adopting a particular beast lord as their totem. The rank within the faith would determine how bestial an adherent appears, ranging through (for example) anime catgirl to 2011 thundercat to Elder Scrolls khajiit. Of course, religious initiation could be replaced with any other measurement system, like tattoos, age, birth sign, etc.

What do you think? Have you done much world building with beastfolk in your campaigns?

Yeah, in D+D, most beast-folk tend to be ad-hoc. The one exception I can think of might be hyenas. Since the gnolls are hyena-folk and they worship Yeenoghu, it could be surmised that they are all connected. My current GM did this for an adventure. Few, if any, other beast-folk I can think of would have connections to similarly themed deities or other entities; at least the ones presented in the official books. Most of the entities and gods tend to be more humanoid. Juiblex might be another possibility, though, as the source for the various oozes and slimes. If you want to have such connections, then you'll probably need to create appropriate entities yourself within the mythos. I think it's definitely something worht doing, though, as it has great potential for contributing to world-building.

2e promoted a lot of the Demon Princes (who sometimes were leaders of beast folk, like Baphomet and Minotaurs) to gods and had a book full of gods for monster days (Monster Mythology)