People often excuse a behaviour if there are extenuating circumstances.
We tend to forgive, downplay or simply ignore it, because we realise that the person doing the behaviour is going through something significant and therefore are ‘not themselves’ at the moment.
If somebody just lost a loved one, they could be excused for having a shorter temper then usual or for crying openly in public. Leaving social gatherings early or for not coming in the first place is completely understandable. Because we know that that person is suffering, we tend to look at their behaviour with more empathy.