[Stevvo]

"I just emailed an invitation to my colleague that we were working together on Zoom"

Most likely explanation is that if you didn't drain the wallet yourself then the only other person with access to your private key did.

[hasangursoy]

He was sharing his screen when I realized the mistake, and he did not even see the keys.

[mmcwilliams]

Was that their only screen? The simplest explanation here is that the only other person you know, even temporarily, to have your credentials used them. Another way to think about it is if you made that first mistake, maybe you made another similar one at some point?

[spzb]

On that screen, he didn't