The reason is that Nissan have spent a lot of time and money on research and development of their Nissan Leaf Electric Vehicle over many years now. From an understandably slow start, pushing into a market that was initially largely hostile to the idea of electric powered cars, they stuck to their guns, continued development and now have a market share to be proud of.

 

Read about the Nissan Leaf 400000 milestone on this link:
https://www.engadget.com/2019/03/05/nissan-leaf-first-ev-to-top-400000-sales/