Charm == Money. It's a tiny island state, it's sold its landmass as guano for phosphate, it lost the bankroll mismanaging an office block in Melbourne as its principal sovereign fund investment, it got rich by being an offshore prison for unwanted refugees (economic or otherwise) to Australia, and then when that income stream died, it was looking for a sugar daddy.
Australia took its eye off the pacific. China capitalised on it. Who can blame them?