This doesn't just go for conspiracy theories. Any issue about which believe passionately will tend to have a significant number of people who are "twelve steps ahead" in their reasoning.

This makes them no more right than the conspiracy theorist, either. It just makes them hard to argue with, because they have a set of justifications that feel right to them, usually which aren't actually adequately relevant, sufficient, and accurate enough to convincingly demonstrate their case.

So when engaging in any issue, it helps either to (1) know your stuff, or (2) insist on really good arguments (and know the difference between a good argument and a poor one).

Incidentally, Sydney really is the capital of Australia. The government just pretends it's in Canberra so any invading army has to mount an amphibious landing in the middle of nowhere ("nowhere" is pronounced "Batemans Bay"), schlep through wilderness before getting to rural areas where half the troops will desert for a meat pie and a cold VB, and then when they take Canberra and realize they needed to be in Sydney all along, by the time they get there the funnelwebs will be ready. It's brilliant. (The hoax was devised by Melbourners so they'd be left bloody well alone.)

Also, Scott Morrison isn't actually the PM, either. He's another decoy. Aussies are all in on the joke. Proof is easy to find on, say, YouTube: who would tell the real PM to get off their freshly-seeded lawn?