I'll hazard a guess that most airline maintenance departments are understaffed because they most likely haven't been replacing retirees. So instead of hiring or paying overtime (those both cost money), they simply stretch maintenance intervals, spend less time doing inspections, ignore minor deficiencies, put band-aids on major issues instead of addressing the problem correctly, etc.
I've been in industrial maintenance pretty much my entire working life, and as you meet people from other industries, you learn that it's the same everywhere. Food production, refineries, chemical plants, manufacturing, transportation, so on and so forth.
They expect people to keep things running by doing less than the bare minimum.
How many industrial and transportation mishaps have we seen the last few years now? Everyone is trying to do way more with way less, which only works until it doesnt.
Even worse: they probably made it a profit center at least on paper.
The other parts of the organization were expected to pay for the maintenance, leading to managers paying less in order to make their own organizations more profitable in order to get bonuses, raises, and promotions.