It's a smart move on their part. A Model S owner is both familiar with EVs and able to afford/have interest in a Leaf. Given the relative success, I wouldn't be surprised if they eventually make a larger EV. Car companies need to play the long game. Treat potential future customers kindly. A lot of them forget that.
I'm going to date myself, but I remember visiting a Lexus dealership when the IS300 had just come out in the US because they had a yellow one out front. I was 16 or something at the time and obviously not in the market, and told them so, but it wasn't busy so we just talked a bit about the car. They offered a test drive just for fun, which I enjoyed a lot. If Lexus hadn't lost their way in the intervening years, maybe I would have purchased one due to the goodwill from that encounter. And maybe I still will, eventually.
Nissan needs to do the same. I'm occasionally surprised when I hear Nissan dealers denying access to their chargers. You're essentially stuck there for some period of time, and they have a golden opportunity to woo potential future customers. Why say no to that and make an enemy?