I'm sure they researched it. And I'm sure it was a minefield.
Existing laws will be written with hotels in mind. If J. Random Startup went to the city and said, "Hey, we want to try this new thing," at best they'd get ignored. At worst they'd be told they'd have to register each place as a hotel, set up inspections, get necessary permits, and generally slit their own throats.
So strategically, the thing to do is to just ignore the laws, find sufficient technicalities and fig leafs to rebuff government on their first approach, and start the service. If it goes nowhere, then no harm is done. And if, as with Airbnb, it takes off, they're in a much better negotiating position.
Now everybody knows what the service is, and it's easy to see that different laws and regulations will be needed. And regulators can't kill the market off without making a lot of people mad. And the city will end up happy: more capacity to absorb large tourist flows, better experiences for the kinds of visitors that would rather stay in a home than a hotel, more money in the pockets of local citizens. And, of course, soon there will be more tax revenue, too.