According to my understanding, the main defense of Bitcoin when it's under 51{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} attacks is to change the PoW algorithm. But why can't a government or a filthy rich person defeat PoW change attempts by doing the followings?

1. Build a GPU farm that has a bigger computing power than the sum of the GPUs in the current mining industry.

2. Build a double-SHA256 mining ASIC farm that has bigger hashrate than the overall Bitcoin hashrate.

3. 51{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} attack Bitcoin with the ASIC farm, forcing a PoW change.

4. 51{88c91daedd271a990a10650c05d769cae2765e0603edf30ca95f18704e5748e8} attack with the GPU farm, adapt to every PoW change, and keep attacking.

It seems to me Bitcoin can be killed.

What's wrong with the method?