Symptoms:
I hit the power button
PSU fan comes on
Motherboard RGBs come on
Case fans (when they were plugged in) all came on
PSU fan comes on
Motherboard LEDs above each RAM slot all come on
Keyboard RGBs (when they were plugged in) all came on

Monitor shows a message saying "HDMI selected" then shows black (but still lit up)

Debug LEDs:
"CPU" turns on and quickly turns off
"RAM" turns on and quickly turns off
then all are off for a few seconds then
"VGA" turns on and stays on until I turn off the system
Motherboard manual indicates this is "Graphics card not detected or fail" (page 43) (troubleshooting guide on page 84)
link to manual: https://www.msi.com/Motherboard/MPG-Z390-GAMING-PRO-CARBON-AC/support

What I've tried:
-tried removing any components noted in next comment (Case fans, GPU, front panel I/O, keyboard, optical)
--additionally tried removing 3/4 RAM modules and leaving just one in slot RAM_2
-tried removing CMOS battery for 5 minutes and then putting it back
-tried shorting the JBAT1 for 10 seconds (while system was powered off and unplugged) (I used a paper clip)
-tried another monitor (also by HDMI. known working but only ever used with DVI)
-tried connecting monitor through GPU (while installed in slot PCIE_1 (it does not connect directly to PSU))
-tried unplugging the CPU_1 and CPU_2 power connectors to make sure they are securely in place
-tried making a forum post on support.msi.com but they IP banned me as soon as I tried to post
-tried putting the driver CD in the optical and connecting the optical, it makes noise for a few minutes but nothing ever shows up on-screen
-tried having USB flash drive with most recent motherbaord drivers connected to backpanel during boot

Always with the same result