For this to happen, the armed forces must move away from their penchant for piecemeal orders. The IA is the worst offender in this regard.
Case in point: LT requirement split into 2.
No pvt company worth the name would want to invest in R&D or even local value addition on license-built products until they can prove RoI.
Both Zorawar and BF's tank use available technologies that cut down on R&D costs. So the only R&D bit is the hull. And whatever R&D carried out is being done on MoD's funds via DRDO. For example, they are developing a new engine and that engine can be used in FICV as well, and the hull is DRDO's too. It uses an American gun and French electronics that are directly imported.
And naturally, if Zorawar ends with just 59 tanks, assuming BF wins the main tender, then L&T would make more by producing 40% of BF's design, while also selling those 59 tanks at a profit.
Overall, the new system has been fleshed out, hence all these willing participants.