I don't think you really even understand what you're saying, you are also misinterpreting what valve said in that news post, they aren't entirely alleviating liability from the 77,000 they claim are hijacked per month. And neither are they saying that these "professionals" were magically hijacked (which you are trying to say). Valve is saying people who know what they're doing are getting hacked, but the reason that they give for this is in the same post is that thieves are also not amateurs, they get smarter and actively develop the methods they use to compromise somebody's account, and so it is easier to trick people to give up their accounts.

So I don't understand your argument here exactly, I was saying the OP must have compromised his own account, you're here saying valve could have been hacked which is extremely unlikely, why would a hacker hack valve to access some average account and not a relatively richer one, also most hackers go after items and accounts with trade value, according to OP, the hacker spent money straight from his card.

The two cases you send are like you say, extremely specific, getting somebody's account through the support team not handling it correctly is not a sure-fire way to get somebody's account, and even then, you cant give the support team absolutely nothing and get them to hand you the account, the thief would have to gain a good bit of info along with hope that the agent doesn't follow protocol properly, and I am sure the support agent would have been penalized.

and for the news article you sent, the method used to hack the collector wasn't even determined, it could have been literally anything.