Historically, .dev has been the realm of programmers who needed a fake domain for programmer testing. The domain never really existed, they just told their computers to pretend it does. But once Google Registry added .dev to their group of TLDs (which include .app and .page) the days of programmers using .dev for testing were numbered.
Starting today, Google is offering .dev as a secure domain for developers and technology. To ensure that .dev is secure, Google just launched .dev and added the whole TLD to the HSTS preload list.