There could be a thousand reasons for his absence but none would qualify as a good excuse.
Here's the bottom line. it doesn't matter. He saved you a lot of drama. Let's say he did you a favor because he is not relationship material. Allow this momentary disappointment to spur you on to finding someone a bit more stable and suitable.
And here's a bit of unsolicited advice: 3 or 4 dates sometimes ..many times... is not enough time to develop intimacies.
Good luck with dating and keep on plugging away.