Not sure how confidential that conference was but I'd imagine these use at least a 2FA dongle to authenticate. This is surprising.
However what Zoom and other conf tools could do is that they could read the password from the URL and then use `history.pushState()` DOM API to replace the URL and erase the password once the meeting is launched.
Downside would be though users wouldn't be able anymore to just copy the URL from browser's URL bar and send to other people to join.