some people do stupid things, and they know its stupid, they know they are being silly and probably heading for a fall... but they blunder through anyway because they don't know what else to do, or don't know how to stop it.
some are just young and have never had to deal with things themselves and just don't realise that things don't always just figure themselves out, as they did when they were kids... as you said, they had no 'real' fear because they thought they'd always be bailed out...
i bet the ones who genuinely had no-one to turn to were less likely to have got themselves into a mess.
but as said, being academically clever and having common sense an forethought are not the same thing.
being stupid and being an idiot are also different things.
the above people have been stupid for what they have done - but they are not idiots... well not all of them anyway!