This is taking the discussion in circles, but the only reason people cared about his ideas was his prior success.

I remember how electrifying Taste for Makers was: http://www.paulgraham.com/taste.html I was barely 18 at the time I stumbled across it, and it made me want to read everything else. That lead to How to Make Wealth http://www.paulgraham.com/wealth.html and What You Can't Say http://www.paulgraham.com/say.html

I didn't really care who he was or what his past achievements are, so at least in my case that proposition is false. I just liked his writing. It's probably impossible to know whether the audience resembled myself or your archetype, but it seems unlikely that hundreds of thousands of people heard about the Viaweb acquisition or about some rich Harvard graduate.

This is much closer to the way I remember it. I discovered the essays before YC existed, and he became one of my favorite writers. I barely knew anything about his online store thingy that he flipped during dotcom mania, and I didn't care about lisp. I definitely thought of him as a thinker that I resonated with.

Perhaps not those events specifically, but even the qualities you mention are byproducts of success. A how-to book on the same subjects, written by different authors of equivalent writing ability, where one is a successful practitioner and the other a fraud, will net you two different books.

While the signals we look at to determine authority are varied and different for each person, style-of-writing is generally included in that list. Why would so much advice on etiquette and morality suggest ensuring one's written communications are of high quality?

I'll admit I didn't really read the links you posted but in looking over the first few paragraphs on http://www.paulgraham.com/taste.html he is clearing signaling his authority in how he name-drops MIT and talks about his MIT educator friend. (And I don't mean to imply there is anything wrong with that; writers are often advised to establish their qualifications early) I imagine the 18-year-old me would have felt confident about his essay simply from this reference.

Finally, the wannabe theory of thought leadership isn't a hard-and-fast rule. There are exceptions...