I'll share my Reddit reply since this is a common miss-conception on why customers are interested in ESXi on Apple HW. Its certainly "smaller" chunk of the overall x86 market from a VMware standpoint, but its certainly not a fringe use case nor miniscule from the customers I've spoken with over the past 7+years having been involved in this space from VMware
If you wish to participate in Apple's eco-system of developing/building MacOS/iOS applications, per Apple's EULA, it must be done on Apple HW platform. For basic development, your standard Apple laptop is sufficient but once you need to build, test, integrate, scale, CI/CD, etc. then laptops/desktops with Fusion on your desk isn't going to cut it for most Enterprises. This is the target audience/use case when it comes to running ESXi on Apple HW and you can either do it yourself like many of our customers do OR you can consume hosted service from MacStadium (who also runs vSphere on their bare-metal offering that they provide to customers). Past customers who've shared their success story and use of MacStadium and vSphere has included Uber, Dropbox, Capital One, Box, Travis CI to just name a few and there's many many others that can't share.
Several years back, I wrote a blog series sharing some of our customer uses cases for MacOS on vSphere if you're interested in some of the specific use case (which are still very applicable in 2020). Simply search "Community stories of VMware & Apple OS X in Production" and you'll see find 10-part series. I would link but don't want to get banned again