With no clue what "computer" and what is inside it that got vacuumed, a blind guess is you no longer have a discrete video card or chip running the video. It is probably back down to the CPU/integrated GPU which is a weak one compared to the discrete one.
If a laptop, then there are BIOS settings for that. Also, the integrated one will always be used with battery power or with a conservative power setting, even with wall adapter power.
If a desktop and monitor, you must have BIOS settings and the correct port connection used.
As far as possible damage, any large motions of dust inside a computer could cause static electricity discharge, shorting of components. I never use a vacuum. At most I do some blowing, sometimes a tiny paint brush.
Cannot blind guess any better than that.
Using flight simulators on computers since 1986, building, upgrading and repairing PC boxes and a few laptops for several decades, building cockpits with several monitors and computers for MSFS 1998, 2000, 2002, 2004, X, and other flying programs.