No one is laying this at the OP's feet. Not at all.
As I said above, there's a reason for his behavior but it is most certainly NOT an excuse. Honestly, I would not have mowed the lawn. I would let it grow to my knees if that was what he promised to do. When he doesn't do it on your schedule and you go out and do it for him, you turn it into a mother/child relationship. You then change the dynamic of this marriage. Yes, the husband was wrong but the OP's response to his neglect of the home is not the right thing either. She is going to turn into his mother.
Having said that, have you ever worked a 12 hour day for a sustained period of time. For most people who are not workaholics, it is soul-sucking, exhausting, and you can pretty much become a monster. My DH has *had* to do spells of it with no choice and many of those times, I've come very close to walking out of my marriage. As soon as the overtime stopped (well within a week or so) he became a normal, rational, responsible person again. After 20+ years of marriage and various "overtime" stints, I now brace myself for when they happen again. We hire a lawn service during those times. But many years ago, we didn't have the money for that so it was just BAD. My house was a mess too. And I got tired of being grunted at.
If this is a recent development in the OP's husbands behavior, I wouldn't read too much into it, let her come here an vent, and hope that it blows over. When he gets more rest, when things calm down with his family, then it's time for "the talk."
