It's ironic that VSCode (best performing Electron app) and Teams are made by the same MS. I know MS is gigantic and these being different orgs but expertise is still inside the company.
I was working for a large company using Office 365 back then. Our teams were using either Slack or Skype. The company pushed everyone towards Teams because it was included in 365 only to eventually backpedal and move everyone to Slack because Teams was an unfinished software. What's surprising to me is that they have had a few years to improve Teams yet its UX is still far behind Slack.
I do believe the lockdowns might have rushed the transition as the UX felt unfinished for years. I can't think of any other reason that might have pushed them into replacing Skype so quickly.