Secondly, you seem to conjecture that attempting password guesses against a network service would somehow bring that difficulty down considerably, to reachable levels. However: local hash guesses are made on GPUs or specialized FPGAs, whereas servers run on regular multi-purpose CPUs—plus, if you had a server respond to login attempts nonstop, it would spend half of the time in context switches and kernel calls. Top http frameworks in pure C reach just over a million responses per second when doing nothing but sending empty responses. You're asking that Steam dedicate a fleet of thousands of servers to facilitate cracking your password. And on top of that, the service would also need a database that likewise serves billions of requests a second.
Additionally, modern hash algorithms like bcrypt are constructed so that they take considerable and configurable time (on any hardware), so the hashing rates are on the order of tens of thousands a second or less, instead of billions and trillions. Since Steam are evidently very concerned with account security, I'd guess they take advantage of these algorithms—and since you changed the password recently, it was probably hashed with the latest used algorithm.
Besides all of the above, a service easily foils password guesses by limiting the number of attempts against an account in a time span, which is by now one of the basic prescribed measures. The whole purpose of ‘password spraying’ is to sidestep this limitation by attacking a lot of users but using most common passwords. In no way does it help with guessing a single long random password.
Lastly, while it's conceivable that Steam could have some vulnerabilities that would make cracking its accounts easier, those wouldn't be burned by attacking the same accounts over and over for months.
To sum up: the whole magnitude of the task is such that no one would solve it just to steal your trinkets, even if they could. It's time to accept that either your passwords are easily guessable, or are lifted from you in some way.
