So I tried using different computers. It turns out that only 1 device of mine exhibits this problem: an Asus laptop with an i9 and Windows 11. This is relatively new to me. I bought it 6 months ago. This device also exhibits high CPU usage on Libre Office when I use multiple monitors. Very bizarre. Fortunately, the process runs on a single core so it only affects that one process. It looks like it's not your code. Sorry to bother you about this. I'm going to experiment more on this by using other browsers like Firefox.
Sounds like you might have some malware (mining bitcoin?) that is impersonating some processes.
Best thing you can do is boot a Linux LiveCD from a USB thumb drive and check if that issue is also happening. If it does, you might have a hardware issue. You should also check out the BIOS/UEFI settings.
Thanks. I just downloaded Firefox. It seems to work correctly. Go figure.
Now I'm going to start poking around at my processes.