It almost always comes down to the user giving away their account information in some way, there were some times an actual hack or some method was used to get around security and yada yada (and probably more but most people will never know about them since companies usually don't advertise these things) but this is nothing new and has been going on for many years and will continue.

I think a big part of it is because most people don't know internet security or just don't care, another problem is the amount of security that is already on Steam that is probably giving a lot of these users a false sense of security that they think they are untouchable thus losing the account / items / money.

I'm neither thanks (I actually am on the other side that dislikes Valves for certain reasons now but sadly they are top so I'm still here. But they all so still do good work in certain other areas.)

If this was not a user issue like you and other people cry about then we'd see top tier user inventories cleaned out not nobodies with mild to low items being sold for crap skins for the little bit of money they have in their Steam wallets. I've been in these topics probably far longer than you and even see many people admit to being stupid logging into sites they should not, falling for TS and Discord scams, using and logging into a public computer like a cafe, and much more.

I give Valve crap when it's needed but I have not seen much or even any evidence that Valve's security is ♥♥♥♥ ad it's not the users that are at fault most if not all the times I see these threads pop up. But think and say what you want, does not bother me since I have more than a brain cell and know what to do and not to do with my account.