... they can't just deflect blame either. I'm sure they'd be happy to take credit for any success. Anyone who had direct control over the product is at fault.
I would not blame an engineer whose experience and training was inadequate to the task unless they participated in the misrepresentation of the app as ready for prime time. The blame lies with the leadership.
Unfortunately, you can often point out failures in software leadership by pointing out collective attributes of the team being led. In a void, I don't think "inexperienced" is describing a fault of an engineer, it's an attribute that describes the fault of their leadership. It's a messy situation, I don't think it's black and white as to who's "fault" any of this is.
Iowa wasn't the only state that planned on using this app. The DNC should have a process in place to validate whatever system is used to elect their candidate.