How do I spy on my competitors

Hi Warriors! What an incredible forum this is. I'm so glad to have found it and am looking forward to being an active member of the community.

For my first question...

I'm creating an info product for a niche that I am very knowledgeable about.

There seems to be very little competition in this niche right now. However, two of the current leaders in the niche who have products similar to the one I am developing appear to be enjoying some very nice success (I have reason to believe that one of these leaders is doing close to 8 figures per year).

The problem I'm having is figuring out how these leaders are achieving their results.

For the 8-figure leader, I'm having trouble finding many organic searches at all for the keywords I would assume he would be targeting. I'm also finding very few PPC advertisements.

The other leader also doesn't seem to be ranked very highly in what I would think would be the desired keywords, although he does have a lot of PPC ads running.

I'd like to figure out what keywords these people are targeting, and what PPC keywords they're bidding on.

Also, if they are in fact doing SEO work, I'd love to figure out which keywords they're ranking for.

If they're not finding their clients through either of these methods, then where the heck are their customers coming from? I know the 8-figure leader also does a lot of direct mail marketing... but the names of those target customers have to be coming from somewhere... right? I've seen his dm pieces and they're not cheap to produce, so I would think they're being mailed out to a pre-qualified list. In fact, the mailing I received says "here's the free info you requested" right on the envelope...which I did request via the opt-in form on his website (which I had to work to find).

Any advice on how I might go about figuring out how my competition is finding, or being found by, their potential customers would be very much appreciated.

Thank you so much.
Madison