More than 10 years ago, the "advertising company" Google started making chips called TPUs. So, what is your point exactly here? As an aside, there is a pretty big boom of semiconductor manufacturing in India (in the planning/commissioning stage) based on a government incentive program floated a few years ago where there's a 1:1 PLI matching scheme by the government (eg: $100M of spend will get you a $100M funding matched by the government). This has resulted in companies like Foxconn at one point deliberating [0] entering the semiconductor manufacturing space in India, besides other local high-market-cap companies like Vedanta and Reliance.
It is important to not leave out the context that Google needed TPUs for their AI development. Now the question is what does Zoho email and office software gain from fabricating custom chips?
10 years ago, Google was already one of the largest companies in the world - and even then they never got into IC fabrication; they had the parts made for them by an established foundry.
Good point about IC fabrication vs creating a chip's design. Anyway, creating a non cutting-edge IC fab is actually not as capital intensive as it may seem, and that there are quite a few fabricators doing >=28nm fabrication.
