Lotus 1-2-3, et al, were killed by MS Office. But Lotus Notes was still selling 20+ million seats a year in 2000.

The web killed Notes, not Microsoft.

Outlook 2003 was a major killer of Notes. Office 2003 on Win2k/XP was a killer offering, MSFT at its height of dominance.

Office 2007 introduced the ribbon and got under pressure by the web (GSuite).

But the early aughts? Office 2003 with XML and Sharepoint just wiped out all other stacks, especially Exchange steamrolling Domino and GroupWise.

I was part of a consulting team back then, the transformation projects were all going in one direction. That stack is dominant to this day.