Why India? Other than being an outsourcing center, India's tech product offerings to the world are almost non-existent; (maybe zoho); without a product and entrepreneurship culture, India makes no financial/strategic sense for startups/bigwigs.
I looked up what UPI was, and it is great that India has it. My guess is either there are lots of Indian tourists/workers in these places so it makes sense to accept UPI. If you consider it as a product offering, more power to you, but doesn't sound like it to me.
If not SF, another American city would have been the tech hub. The enterprise and consumer markets were in the US. The tech companies served those customers. Or at least they used to. Now with corporate financialization and the rogue administration and supreme court, the US is rapidly destroying itself.
UK did this shooting-itself-in-the-foot thing called Brexit. So (outside of ARM, and forex), the main reason to go to UK is to setup a surveillance solutions business, or data harvesting business like Palantir.