So when an organization wanted to develop a Web map presence, they had a choice to make on which Web API technology to deploy. Since there wasn’t a lot to differentiate the technologies, the selection often simply depended on the technology that the developer was most familiar with. Sometimes, it depended on the existing technology framework within the organization. However, each of the three major API technologies had their benefits and drawbacks.
In 2011, Microsoft surprised the software community by announcing that Silverlight development was being ended. Adobe followed suit saying that their Flex development would end soon and that the Flex software would be moved to open-source status. The problem at that time was that the W3C was still furiously getting HTML5 approved and implemented by their members. Since both Flex and Silverlight require browser plugins, the attraction of native HTML5 was strong as it could provide a cleaner common interface in most modern browsers.
In my opinion, a single Web map API technology is good for the community, for both developers and users.