Its not that odd if you think about it. Everything else in this universe is deterministic. Well, quantum mechanics, as we observe it, is probabilistic, but still governed by rules and calculable, thus predictable (I also believe it is, in some sense, deterministic). For there to be free will, we need some form of “special sauce”, yet to be uncovered, that would grant us the freedom and agency to act outside of these laws.
Its worth mentioning that certain mainstream interpretations are also concretely deterministic. For example many worlds is actually a deterministic interpretation, the multiverse is deterministic, your particular branch simply appears probabilistic. Much more deterministic is Bohmian mechanics. Copenhagen interpretation, however, maintains randomness.