Unfortunately, the Nexus 6P had an Achilles Heel, and that was a bootloop issue. Google acknowledged at the time that this was a hardware issue, and it’s thought that the Snapdragon 810 chip was ...
Whatever the case, Google lost its footing after that. Three more Nexus phones were released through 2015, including the Motorola-made Nexus 6 and Nexus 5X, and the Huawei-made Nexus 6P.