daijoubu

You can adjust the landing sensitivity and the amount of time after detecting a landing that it will auto disarm. Default is 1000 mS. https://github.com/iNavFlight/inav/blob/master/docs/Settings.md#nav_land_detect_sensitivity

When in failsafe, you can't disarm, because the flight controller is no longer able to communicate with the receiver so it never sees your command.

I don't know how landing detection works in betaflight. In Inav, it needs to see a moderate thump while the throttle is low. 1s later, it will disarm. I'm not...

Usually that is the arm switch, but for remote disarm to work, you need a reliable control link.

It is configurable, but the default is failsafe. There are options to allow automated flights to continue even when a control link is lost, but they are not the default....