Many men like this, like to have "options". So if they are single, or even if they arent single, they will attempt to line up a few options, that they have on standby should the urge arise, or should their current bit of stuff fall through.
The leading you on and getting you keen, and then not seeing it through is a classic sign of this.
I have learnt the hard way, that if a guy is really keen, he will overcome obstacles to be with you. If he acts keen and then offers lame excuses, then he is just using you as a back up or a fill in. If you make yourself available, he will use that.
Steer clear and find a bloke who will make the effort that you are worth.