What sort of things were overlooked by the community that caused this site to fall short?
The main issues were/are :
I personally believe that the site should have been given a warning, and then some time to tackle these problems, however, that did not happen. Nonetheless, we created some excellent content, that will find a home on EE now.
I do feel that it is (at least partly) our screwup, but that's not the reason I'm quoting this.
Basically, being a subset scope-wise, we had much higher standards to live up to. It was uncertain if we would even have had a private beta, so once we had one, we should have put more effort into proving that it would work. Our questions/day were rather low -- on its own this should not have been a problem, as Chem.SE had similar stats in its private beta. However, we also had a very small group of answerers, and we had low views.
I don't know what we could have done. Some of us delayed answering to let others answer, but that didn't work much. (Also, on other private betas it is quite common to have 4-5 answers on good questions. Here we had just 1-2). I guess this was just a general problem with the community; only a few had immediate questions to ask. It could also be that Arduino.cc and Google manage to solve most Arduino questions one has, and the site just wouldn't have worked as a private beta.