3 Wheeler EVs are booming because the prices are very low and allow you start your own business by undercutting Auto Rickshaw unions. Your average auto rickshaw or e-rickshaw driver can make around $150-200/mo tax free and eligible for subsidies, making it more competitive than working at a factory ($250-300/mo but 5% income tax and not eligible for subsidies). This makes EV 3 wheelers attractive as it's an investment in a small business.
On the other hand, EV cars aren't as popular in India yet due to range anxiety. Price doesn't factor as much because the tax incentives are made to incentivize EV cars (50% tax on disel/gas cars bit 5% tax on EV) and EVs are fairly affordable (a starting model Tata Tiago EV is around $9-10k) but no one trusts EV charging infra in India, so people are delaying purchases in order to buy a premium diesel car (eg. Toyota Fortuner, Mahindra Thar), eat the tax and buy a $4-6k Renault or Maruti ICE car for $9-10k after tax, or just keeps driving their gas car. This will change in 10 years, but the future is looking Hybrid, especially because Toyota is looking at expanding in India and lobbied a drastic tax cut [0]
No one actually buys 2 wheeler EVs - you can save $1-2k more and buy a luxury 2 wheeler like a KTM Super Duke. Most electric 2 wheeler sales are driven by Ola (India's Uber/Doordash) subsidizing it's drivers and deliverers to buy an Ola manufactured 2 wheeler while working for Ola.
[0] - https://www.reuters.com/business/autos-transportation/toyota...