Internet interruption and FC doesn't launch?

I had this strange thing happening.
My Internet provider had a problem so I had no internet connection.
Tried to launch FC, AE, Affinity photo and designer and they would not launch.
My whole system struggled to work and was extremely slow.
Has anyone experienced this and why would this happen?
All my files are on external drives.
Internet came back and all is OK again.
Bewildered!

Was it down completely or just very, very slow? Generally a good idea if your ISP is having problems is to disconnect your computer from WiFi. All applications ping the mothership when they launch. If you're offline it ignores the check. If you're slightly online, the ping might go out, and the response doesn't come back in an expected timeframe, and the application shuts down. Happened bigly on the Big Sur rollout because of Apple server problems.

Completely down. Not using wifi but Ethernet.
This is the type of mystery you discover when the event happens.

You can check to see if it is a possible ongoing issue by disconnecting the Ethernet cable and disabling any WiFi connections. Then launch the programs to see if the issue is repeatable.

A computer can get hung up on trying to re-establish an Internet connection and slow down badly. A simple re-boot should fix everything, or turn off networking.