I understand that the hardest part is that he made all these big moves, got you feeling like he was invested in you, then went cold. The contrast in behaviour is confusing to us on the receiving end. It sucks.Why do they say things they don’t mean?! Why do they make promises they have no intention of keeping?
Unfortunately, the only answer I've ever found is that he's subconsciously using me for an ego boost. It gave him power that I believed his intensity came from a real connection, that I would follow his cues (like you did when you mentioned it to your family because he led you to), and it gave him power when he got bored and left, when he decided to come back nonchalantly and knew I would reply to his message even after a long absence.
I've found it's always about power and control. The love bombing is just empty words to him but he gets a kick out of how easily he is believed and can get the other person invested.
I took too long to learn my lesson, I'm glad you've made a quick decision.