Well, actually there are three interrelated phenomena: IoT as a technology phenomenon, IoT as an application phenomenon and IoT as a marketing phenomenon.
As for the first, IoT is a multi-decade convergence of technology trends: constant substantial cost reductions (Moore’s law), maturation of interoperability and standards, ubiquitous connectivity (especially for wireless), and ease of implementation (stuff just works off-the-shelf). The many devices and components comprising the IoT had cost many thousands of dollars a couple of decades ago and now cost a few bucks or even pennies. That trend will continue for decades to come. As the components get ever closer to zero cost, IoT capabilities will be built into more and more objects.
Timely, incisive articles delivered directly to your inbox.