My best guess is that the pandemic is what happened — if this story is true.
The bundling didn’t matter when no one needed a large amount of seats for an in-office workforce.
But during COVID and currently, there was no better pricing than what Microsoft is offering for all the things (ex. Azure + 0365 + GitHub).
The market shifted from Slack, Zoom and <insert anything else here> to Teams for large enterprises when they recognized that no one was coming back into the office.
Source: I bought enterprise software for a Fortune 20 during COVID until I launched my startup.