[BroJoeK]

"Russia's financial and technical resources are grossly inadequate to building the fifth-generation Sukhoi Su-57 stealth fighter on the announced schedule -- and especially so without India participating in the project."

Agreed.
Russia & India have been dance partners for many years, hard to understand why, easy to suppose Indians ready for different music & a new partner.

[Rockingham]

I suspect that India’s politicians and bureaucrats find that Russia is an easy partner in the graft that tends to invest the Indian procurement process.