Why would a manager at Nissan allow this to be built? They now have to maintain two parallel versions of their complex site. What is the non-ideological payoff?
A couple of reasons:
1. It fits in with the brand: hip, innovative, and next-generation.
2. It launched at roughly the same time iAds did, which featured the leaf, which likely drew a ton of mobile traffic, and since this works on iPad & iPhone, it makes Nissan look fantastic.
3. They don't have to maintain two versions of the site, the studio that they paid to do the coding does.
Big brands like Nissan have a large budget to spend on the latest and greatest, and they do it. The studios that do the development are allowed to try new things, and they do. For Nissan, they get a site that looks fantastic, comes in on budget, and garners responses like this thread. The studio that does the work gets to add a site like Leaf to their portfolio of work, and their designers and developers learn a new skill that can be transferred to other high paying work. A win for everyone really.
In case it was unclear, this is a serious question. I'm wondering why a business would build a complex HTML5 site if they're going to have to build a flash version anyway.
That manager must have spotted that there's a vocal minority on the interwebs, who will be blown away by one of the versions and drum up interest to their page at a marginal cost of 0 dollars.
I wouldn't have visited Nissan's web page today, or any time soon. But I did, Nissan owes that guy a nice bonus.