Being a first time, or even just smaller developer is a nightmare when you compare it against large companies.
You basically don't have a chance if you try to carry your dream yourself, because you lack funding. But getting in bed with larger companies for funding and marketing puts an insane amount of pressure to perform well or go under.
I can totally understand why so many things were over-promised. I can't excuse what we got on release, but I do understand why he lied, even in the weeks leading up to release where everyone who plays immediately knows what's bullshit.
And to be honest, I would likely do the same in some situations.
Like the multi-player aspect where supposedly you would be able to see each other in-game. They really thought with the size of the procedural generation it would take a lot longer for people to meet, even if they were trying to meet up. Unfortunately they forgot to take statistics and probability into account. With the large amounts of people playing, two were bound to end up close enough to meet in the finest few days.
I think they really thought they'd have time to fix it before anyone met.
You'll say anything when it's your future, and the futures of all the people you work with, on the line.