hdmi / dsi 출력 설정에 무언가 영향을 줘서 DSI로 강제 설정되며 HDMI가 꺼지는것으로 추측.
display_default_lcd If a Raspberry Pi DSI LCD is detected it will be used as the default display and will show the framebuffer. Setting display_default_lcd=0 will ensure the LCD is not the default display, which usually implies the HDMI output will be the default. The LCD can still be used by choosing its display number from supported applications, for example, omxplayer.
The Raspberry Pi Touch Display is an LCD display which connects to the Raspberry Pi through the DSI connector. In some situations, it allows for the use of both the HDMI and LCD displays at the same time (this requires software support).