NCSA is a fairly free-form environment..and we certainly had the resources, the money, the machines and the network to be able to do interesting things.
Even as late as '95, the Net was populated by early adopters, defense contractors, techies, and academics. It was completely unclear whether it would spread beyond that to consumers and business users.
So, then I met Jim Clark and we started talking about various things we could do and it made a lot of sense to try and do that in the context of a new company.
The first alpha version came out in January of 1993, and the first beta version came out in March. But the real launch was in April 1993 when about 10,000 people started using Mosaic.