Only an idiot, or someone who intentionally stuck their head in the sand, couldn't see there was an issue at Gox years before it went belly up. Why people put money there I have no idea. Maybe it wasn't obvious what the problem was (we have more details now) but there was something off and it was only a matter of time. I got the feeling there were a lot of naive younger people who had money/btc there.
It was adviced by plenty of people in the community including Andreas Antonopoulos that people should never put their coins inside anything that isn't their own wallets that the control. People that got scammed by Mt Gox wouldn't listen so it's their fault, they took a risk and they lost, that's how it goes.
It is not so hard to imagine that bitcoins stored in online wallet/service will be hacked sooner or later. There is NO guarantee and no measure that will keep coins stored that way safe.
Only a extreme fool or an ignorant keep his coins that way. There were hacking attempts (successful!) on bigger services that MtGox in the past (not necessarily bitcoin related) and those who believed that their coins are safe there were daydreaming.