There are other things running in the background, usually windows service processes but, they shouldn't be causing 80% cpu usage. You could try tuning up the system by going through a windows service optimisation guide. Don't disable windows update or windows defender.
You may also some have 3rd party apps installed as services, both origin and steam have client helper services, for example, could be anything you may have installed similarly.
May also be a malware infection, I'm not up to date on the latest scanners and whatnot, but you can run
autoruns to see what bloatware or if any suspicious processes are running, that is processes lacking any description.
There are also malware guides about but often involve running several different malware scanners & I've heard it said
Clam Av is pretty good but I don't know all there is to know about it, I don't think I've had any malware lately.
Hope you've got a fast ssd. Could also run
Wise Reg Cleaner that also has some system tuneup options. You could find bucketloads of software free or premium that does all similar things so that would all entail reading around to catch up with the latest developments.
The latest nvidia driver was patched to 430.64 to fix a security hole if you're on nVidia you might want to update that.