The hidden problem many password managers gloss over is how unbelievably insecure the Windows copy-n-paste is in Windows for decades.

IIRC (corrections welcome) Windows's window manager broadcasts the contents of the "copy" operation to any application that requests to receive the ? WM_CLIPBOARDUPDATE event... so any windows malware or even legit application with legal fineprint basically gets a plaintext message with the contents even before the "paste" occurs. All running apps are trusted.

Here's an example blog entry from "grumpy-sec"(?) laying this out (2018): https://share.google/0til1YzbF4xFRY7ls

Not to mention newer Microsoft conveniences like logging your clipboard history to your disk so it doesn't go away when your computer reboots, and/or syncing it to the cloud.