Published on 12, July, 2020
Maybe when his friend asked him to hang out he didn't feel he could refuse - this might be the case if other friends have deserted him in the past for not doing what they expected. He might feel more secure in his relationship with you and more comfortable saying he would prefer to still see you at a later time as planned. Or maybe his friend suggested doing an activity that interests him, that you aren't interested in, and he felt that doing that activity would be relaxing.
I'm just guessing here though - best way to know is just to ask him.