I download files and it does not show in my download folder until about a min later. It shows up in file explorer immediately. Any idea what could have caused this?
Antivirus, most likely.
But I did not change or install any new anti virus recently though. It happened only recently.
Antivirus updates itself constantly, and scans of commonly downloaded files like installers can take a long time. It's almost certainly that.
Defender has been causing problems recently due to a refreshed code-signing certificate as well. See Problems caused by Windows Defender (strange behavior when using Opus)
Try disabling it and see. It doesn't take long, and would prove or disprove the theory.
If the problem is still there even with the virus scanner disabled, see this FAQ for other possibilities: Changes to folders are not being detected