Keep in mind there is a whole spectrum of what constitutes thought leadership. Several times, I've had clients say, "Last night I was looking for X and I found a great article on it. Turns out it was something you wrote!"
Another organization was going through their contracting process with me. One of their managers later told me that when they Googled for my name they were blown away by the size of my online footprint. Most of that was simply 10 years of blogging a few times each month about whatever topics I was finding interesting.
Also based on my blogging, I've had fairly well-known companies interview me for their blogs or webinars while using descriptions like "one of the worlds leading experts in X." This was all based on years of blogging on the topic.
Another great way to be viewed as a thought leader is to write a short book. Imagine you are looking at hiring two candidates that both look good, but when you search for their names you find that one has a book for sale at Amazon on a topic of interest to your company. It is a very strong way to market one's expertise.
Joel on Software, patio11, DHH, Seth Godin, Tim Ferris, countless SEO blogs, and so on in increasing order of cringiness.
It is the whole modern melting of personality/advice/authority/promotion .
Some are really sincere some are really good at faking it.