I've talked about this with a co-worker. We've come to the conclusion that since they don't really have a bench the starters figure they have to stay out of foul trouble and the easiest way to stay out of foul trouble is to not play any defense. It's also less physically demanding to not play defense, so they don't need the rest that a good team that plays defense needs. Also, not working so hard on defense in the first half keeps them less tired and when you are tired you commit the silly fouls.
Then in the second half, each player has either one or no fouls and they can play harder with less chance of fouling out. They don't need as much rest because they didn't expend as much energy in the first half. This allows them to come back from deficits with the short bench they have.
I've watched several games of theirs this year and that seems to be the mentality of the players.