Excuses have a short shelf life. By next week nobody remembers them, but they remember the result.

Reasons feel enormous while you are giving them and then evaporate. A week later the group remembers that the slides were not ready, not that your laptop died on Tuesday. That is not people being unfair, it is just how memory works, since outcomes stick and context does not. So the story you tell about why matters far less than it seems while you are telling it.

If something is going sideways, spend the time you would spend explaining on whatever can still be fixed. Tell people early and keep it short. A brief warning plus a result beats a long account of the reasons.