One reason for the explosive interest in service mesh over the last 24 months that this article glosses over is that it's deeply threatening to a range of existing industries, that are now responding. Most immediately to API gateways (eg. Apigee, Kong, Mulesoft), which provide similar value to SM (in providing centralized control and auditing of an organization's East-West service traffic) but implemented differently…
I was going to say re: "How is this different from an API Gateway?" – this was a lot harder a question for me to get my head around than William suggests, _because_ API Gateway vendors, I'm sure quite intentionally, have been positioning their stuff as service mesh solutions or alternatives, not as service mesh complements.
And I think it is more akin to have an aircraft carrier and the protection fleet of smaller ships..
You have your big api gateway with management, billing, governance (for B2b, b2c, b2b2c) and your service mesh.