Answering this in any detail would almost certainly dox myself, but I have a PhD in a hot topic that was nascent and not in vogue when I started, so my thesis w

Answering this in any detail would almost certainly dox myself, but I have a PhD in a hot topic that was nascent and not in vogue when I started, so my thesis work was immediately useful to lots of companies and there are very few other people who are experts in this niche. On top of that I have some deep industry background in a key application domain that, again, few other people with phds in my particular niche know anything about. (By deep I mean "hard earned knowledge about all the gritty details", not "spoke with a guy about it in the office once") The topic is more popular now and funding agencies are starting to fund more graduate training in this area, so my current moat won't exist forever. But by then I'll have dug my current moat deeper, hopefully.