Many monitors (even some name branded ones) sadly do not support(/are configured correctly) DDC, a protocol which allows detection of monitors.
Using the explicit CRT naming scheme one request linux to ignore what monitors it detects and go by what you specify as existing. This takes awa the problem of auto switching while using a KVM
ConnectedMonitorWith this option you can override what the NVIDIA kernel module
detects is connected to your graphics card. This may be useful, for
example, if any of your display devices do not support detection
using Display Data Channel (DDC) protocols. Valid values are a
comma-separated list of display device names; for example:"CRT-0, CRT-1" "CRT" "CRT-1, DFP-0"
WARNING: this option overrides what display devices are detected
by the NVIDIA kernel module, and is very seldom needed. You really
only need this if a display device is not detected, either because
it does not provide DDC information, or because it is on the other
side of a KVM (Keyboard-Video-Mouse) switch. In most other cases,
it is best not to specify this option.