It's very easy to disagree with him, because the server market doesn't work the way he think it does.
Google, Amazon, Microsoft and Facebook collectively purchased 31% of all the servers sold in 2018. The market for server hardware is dominated by a handful of hyperscale operators. The "long tail" is made up of a few dozen companies like SAP, Oracle, Alibaba and Tencent, with the rest of the market practically representing a rounding error.
These customers are extraordinarily sensitive to performance-per-watt; for their core services, they can readily afford to employ thousands of engineers at SV wages to eke out small efficiency improvements in their core services. They aren't buying Xeon chips on the open market - they're telling Intel what kind of chips they need, Intel are building those chips and everyone else gets whatever is left over. If someone else has a better architecture and can deliver meaningful efficiency savings, they'll throw a couple of billion dollars in their direction without blinking.
This is not theoretical - Google are on the third generation of the TPU, Amazon are making their own ARM-based Graviton chips and Facebook now have a silicon design team led by the guy who designed the Pixel Visual Core. It's looking increasingly certain that Apple are moving to ARM on the desktop, which further undermines the "develop at home" argument.
ARM won't win the server space, because nobody will win the server space. With Moore's Law grinding to a halt, the future of computing clearly involves an increasing number of specialised architectures and instruction sets. When you're spending billions of dollars a year on server hardware and using as much electricity as a small country, using a range of application-specific processors becomes a no-brainer.
All of this costs money, in terms of either having more developers/testers or having longer development time. So, in order to justify this investment, the second platform must be way cheaper in order to cover costs for extra developers/development time. And if there is a such huge difference and second platform works great, then why still have support for first platform anyway. Ditch it, and you will save yourself some money.
You could be an ISV, but again, your software will be more expensive if you need to support two different platforms. Which means that your customers must be willing to pay for it. Which brings us to same conclusion, unless there is a big saving by running software on alternative platform, nobody will care.
Google's data centers collectively use more electricity than the state of Rhode Island, or about the same as the entire country of Costa Rica. Their electricity consumption has doubled in the last four years. At average wholesale prices, their annual electricity bill would be about a billion dollars. ARM isn't dramatically more efficient than x86 in most applications, but specialised ASICs can be orders of magnitude more efficient.
I'm not saying that nobody cares about the choice of architecture, I'm saying that major tech companies with vast quantities of servers are beginning to develop their own silicon with custom architectures and custom instruction sets, precisely because that's vastly more efficient than using a general-purpose architecture that happens to be popular in the wider software ecosystem. The fact that nobody else uses that special-purpose architecture is unimportant, because it is economically viable for them to invest in tooling and training to write and port software for these weird chips.
Are Alibaba and Tencent Really in the long tail? I believe Tencent could be since it is about 3rd of the size of Alibaba, but if I remember correctly Alibaba will overtake Google by 2019 ( They had ~90% growth in 2018 ), and 2018 were already close to matching Google's Cloud Revenue.
I wonder if OVH is also big in the list. And Apple? Surely the Server Back End to services 900M iPhone users can't be small. How do they compare to say, Google in Server Purchase Terms?