Generally, yes, companies do blog posts for marketing.

It gets a bit...missing forest for trees?...when viewed solely through the lens of "cui bono? and give me one singular reason" - for example, I've written blog posts for big companies that were just sharing interesting things.

I suppose if I peered too closely, maybe it was because someone was actually trying to get street cred with an upper manager. Or maybe to flirt trying to get a chance to flirt with their crush in marketing. Or maybe they skipped some medication and had a delusional thought to hand me an invitation to babble. :)

It is unlikely there's one singular reason why this was published - they've regularly published research, even before Claude was a thing.

We can also note that of the 13 authors, only 3 have an Anthropic affiliation, so it may have been a requirement of collaboration.