I think the key mistake was that Hyun thought he could delay the hydra break before PM got storm. Unfortunately, Hyun might've not realized that PM skipped sairs entirely, and went straight for templar tech - archives was already up the first time he made a pass with his hydras.
The question I would have is whether or not it's obvious someone is skipping Stargate if you haven't seen Corsairs at that point in the game. Obviously, Hyun had no Spire to scout, but I think at top-level, that should be a process of elimination.
Had he figured that out, I'm sure he would've committed more towards economy/tech, meaning more defense + Hive tech by the time PM attacked. Especially in light of PM lacking +1, he would've been in a commanding position at that point had he held (4 bases to 2, just sniped a shuttle drop, etc.).
He sniped one Reaver, stopped a lot of mining, a few probes, a few goons and he's got his nat coming up faster, at the expense of his own goons and having slower tech.