Why does connecting Monique through the mother game still start?

Question

Video cards

Hello, first about the hardware.
Monique - old with a VGA connector
Motherboard - socket 1151 (supports VGA)
Video card - GT1030 (supports Dvi-d and HDMI)
And an active adapter from VGA to HDMI
Now, to the problem. The adapter burned out -> I can not connect the vidyuhu. Connected Monique to the motherboard. The brother, not knowing the story, sat down to play. The game started and the FPS, as with the whole adapter. Why?

Answer 1

The GT1030 processes and sends to the integrated one, which already outputs the VGA signal.
UPD:
GP1 Diskretka
GP2 Embedding
Situation1: The game is running on a monitor connected to the motherboard. 22FPS
Situation2: The game is running on a monitor connected to the video card. 26FPS