"All of a sudden"? I've heard that term used for probably twenty years now, if not more, originating (IIRC) with Warren Buffet. What does the moat of a castle do? Keeps the baddies out. What does the "moat" of a business do? Keeps the competitors out. To take a recent example, what would Nvidia's moat be? A strong argument could be made that it's CUDA. For the sake of argument, let's say anyone could throw a bunch of silicon on a PCB and make a GPU equivalent to Nvidia's. Doesn't matter, because your cheapo GPU won't run the CUDA software that makes Nvidia's dominance possible.
To offer one more example out of my butt, take Apple. The Apple brand makes up at least some of their moat. You could build an exact clone of an iPhone that even runs latest iOS (assume for the sake of argument that there's a way to get the OS on your hardware). Doesn't matter, unless you're ready to infringe on trademarks by putting an Apple logo on there, few will buy it because they want Apple, not a functional work-alike.
To offer one more example out of my butt, take Apple. The Apple brand makes up at least some of their moat. You could build an exact clone of an iPhone that even runs latest iOS (assume for the sake of argument that there's a way to get the OS on your hardware). Doesn't matter, unless you're ready to infringe on trademarks by putting an Apple logo on there, few will buy it because they want Apple, not a functional work-alike.