Your flag was a recommend closure flag. Those don't go to moderators, but to normal users in the Close Votes queue.
Those flags are marked declined if three users in the queue review to leave the question open, without a single user voting to close. In fact, that's what happened here (the fact that a moderator made one of the reviews is irrelevant).
Quite frankly, I think the close reason is applicable here, as installing Android Studio is a matter primarily of concern to developers, which the close reason says is off-topic. I'd ping the users who reviewed this in chat asking them why they thought the close reason wasn't relevant.
Do note, however, that while this is common enough that we have an FAQ written on the topic, it's sufficiently rare an occurrence that doesn't really warrant adding more complexity to the system. I can see some possible edge cases with this, and a single declined flag won't affect things very much. (While a similar mechanism does exist with spam and abuse flags, to retroactively dismiss a helpful spam flag as disputed, that mechanism is used often enough to warrant it. As these flags can result in massive reputation penalties for the post authors, moderators may need to reverse it in case they're used inappropriately.)