As an Apple user, you might be used to everything working reliably, but based on my experience over the past 10 years working with HiDPI displays (such as Dell UP2715K = 5K or Dell UP3218KA = 8K, and later with Apple Studio Displays = 5K), I can tell you that you can forget about everything always working smoothly during the handshaking process between the GPU and the monitor. Even if you use the best connection cables, the connection process is always on the edge, and there can always be a synchronization issue, causing the monitor to remain dark and requiring the Mac or PC to be restarted to reset the display connection between the GPU and the monitor and attempt a new sync.
I always have to smile when more and more users notice these situations and only very slowly realize that this is absolutely normal these days.