This was possible only by the master game-plan of launching commercially with absolutely free usage for 8 months (5-Sep-2016 to 30-Apr-2017). Had they rolled out even with half the pricing of the then rates (Rs 250 for 1GB), they wouldn't have survived. Many players such as Tata DoCoMO, Aircel, Uninor were already providing same benefits at half the cost, yet they vanished.
The guy/team; who innovated this idea of twisting TRAI rules, launching a "Beta" service, bypassing TRAI rules and charging Rs 0 per month commercially for a straight 8 months; would get a huge appraisal today.
In an already saturated market like India, launching a service and marching towards the top spot is certainly laudable. Not sure if all what they did was legal, ethical and justified. But thats how one does business in India, right?