> the Ukrainians themselves saw the huge army on their border and told everyone it wasn’t going to happen and refused to build any defences

You're going to have to cite that, because Ukraine was already in the low-intensity Donbass conflict when the most recent invasion happened.

But yes, you can't hide an invasion fleet. The Chinese navy only has three aircraft carriers. They've recently had high level purges in the PLA. Invading now would be a disaster for them. But you never know when a disaster is going to get ordered for political reasons.