I been setting up a Rpi 3 Model B to control some servos so I planed to use a PSU to power the servos since they will draw too much current for the pi to handle.
At this point the setup is as follows: the pi is powered by its AC adapter and is connected to a monitor by a HDMI cable. The pi's ground is also connected to the PSU's ground and the PSU's output is not connected to anything. All of them (the pi, the monitor and the PSU) are connected to the same outlet. The servos are not connected yet.
Then I turned the PSU off and the monitor screen blacked out only for a second. The pi didn't reset and everything seems fine.
What could have happened?