Why is China smashing its tech industry?

It exists fundamentally to reduce rent-seeking, which is why it exists in some form or another in every economy where there is strong government control of housing. If you remove the Hukou system, everyone will flood to the cities, and you will have overpopulation. You can also liberalize housing, in which case people will pay around 30% of their income in rent which the CCP think is not economically productive. This happened in Beijing and Xi has been floating the idea of literally building another city and moving industries there to reduce rental pressures.

Or you limit migration into the cities to the speed of new constructions, which enables you to set a low rent and, according to the CCP, have better economic outcomes. You limit migration by disincentivizing people who move to the cities without following the quota, hence the Hukou system.

As far as incentivizing Han migration, I can't speak to recent efforts, but for a long time Han migration was incentivized because, well, there weren't much people in Xinjiang and there were a lot of resources and a border with the now-hostile USSR that needed to be exploited. So the CCP under Mao did everything they could to get as many people into Xinjiang. That included allowing Uyghurs to have 3 times as many children as the Han. But otherwise if you need more people into Xinjiang they're not going to be Uyghurs because, well, they're already in Xinjiang.

Literally all you need to entertain people is talent and a space.

China considers Australia to be within its primary sphere of influence (a rapidly expanding sphere as far as China is concerned, as they push outward militarily).

Japan was willing to invade Indonesia, Malaysia, Papua New Guinea and Australia during its Empire days. China is a drastically more potent superpower than the Empire of Japan ever was and China's military reach will be far greater.

In an Asia war scenario (which is what we're talking about here), Australia is absolutely on the table to be invaded by China. It's a prime candidate if China's foes attempt an inevitable resource blockade (which would see the BRI targeted early on). Invading Australia also disables a critical, reliable ally for the US side. The US & Co. would need vast regional resource supplies to sustain for long at all in a conflict with China in Asia; China would know that, and would understand that Australia is one of the most important resource suppliers both regionally and globally. At a minimum China would seek to cripple Australia functionally, and an invasion is ideal toward that ultimately (otherwise the Australians would just keep rebuilding and repairing damage).

European empires would never seek to conquer territory in Asia, it's too far away. Britain would never seek to conquer India, it's too far away.

China sends its vast fishing fleets to illegally plunder South American fishing waters. It has blanketed much of Africa for resource extraction purposes. It certainly considers Australia as a resource target within its reach. And it's more than that, China had already fallen into the mindset of considering Australia to be increasingly within its sphere of influence and control, which is why the CCP has gotten so angry at Australia in the recent political-economic conflict between the two. They had plans for Australia and assumed they would be dictating terms going forward.