Jio's network infrastructure is far advanced when compared to other operations. They didn't just build it by keeping 4G in mind. It can support 5G and follow up generations without a lot of modifications. Incumbent operators had to upgrade their 2G/3G infra to support 4G. In fact, lack of 2G/3G service is a reason why Jio doesn't operate in Andaman & Nicobar islands where it's mandatory for operators to support 2G/3G service.
> But what exactly gave them enough confidence to go ahead with Jio, a deep discounted mobile network.
I would say it was access to funding and top-level infra. Not to forget, the industry was stagnant when it comes to high prices.
I included the fibre optic network because most of the other operators don't have a high capacity network like that across the country. Owning your own infrastructure allows you to undercut your opponents because you don't really have to ameliorate them to get access to their infrastructure.
Reliance just like any other telecom operator was laying cables which they could even lease to other private players.
But what exactly gave them enough confidence to go ahead with Jio, a deep discounted mobile network.