The problems you described seem to me like they have nothing to do with screen time and everything to do with consistent, attentive parenting. We definitely agree that that is crucial.
Sure, it's not as simple as having one isolated reason, but would you expect the same outcome if you replaced the iPad by books and leave everything else the same? I'm having a hard time imagining this. Yes, it's multiple factors coming together, but nothing beats the destructive impact of too much TV/smartphone/tablet on little kids, except maybe severe abuse or actual drugs.