Question Can't see anything on screen, but there is signal to the monitor

Nov 15, 2021
I recently built a pc using new parts and my sisters old gpu and psu, because her pc broke after she blacked out, she spilled water on the pc. I tested the psu and gpu and it worked, but I'm assuming the parts are still faulty. Recently I was playing f1 2020 and it kept on crashing, the gpu would suddenly spike to 100% and the game would crash. This shouldn't happen, since I had a 1080ti and was running it on low settings. I underclocked the gpu and it would work for a bit, but still crash. Unfortunately, I was playing and the entire pc crashed, and afterwards the pc wouldn't start up. Currently when I hit the power button the gpu doesn't light up for around 20 seconds, with the motherboard showing the vga light but after a bit the vga light goes away and the light on the gpu goes on, seemingly working. Unfortunately, the monitor stays black, but strangely there is a display signal. I have checked that the monitor works, but I cannot check whether the psu or gpu is the issue.
Specs: Nvidia gtx 1080ti zotac
CPU: Ryzen 5600x
32 gb ddr4 ram 1 tb ssd
Not sure about power supply brand lol but it was 750 watts gold
gpu and psu are about 2-3 years old
Another thing i forgot to mention is when I was downloading the game the entire disk was at near 100% and the computer was super slow, and when I did benchmark test the cpu ram and gpu were all underperforming.