Can anyone tell me what impact their whole government dying at once in a plane crash had on this?

Would they probably be doing better or worse if those people had stayed in power? Was that a significant factor in this?

Opinions will vary. Most people on that plane (not all) represented the equivalent of UK Reform party - isolationist, backward-looking, populist. That party, ironically called PiS (Prawo i Sprawiedliwość, Law and Justice) brought in a lot of reckless spending and anti-growth measures. Still, GDP rocketed on under their government just as much as under the other ones. As did inflation.