So what will it take for BTC to becomes a "mainstream" asset?

Whatever XiJinPing's analysts thinks will work toward its objectives.

China accounts for 66% of Bitcoin mining and as large or larger shares for practically every other coin requiring PoW cryptographic algorithms to build blocks. If you include the Mongolia and Russia, you get close to 100% of mined crypto. Even if the location of the rigs was more evenly distributed, China still has a strangle hold on the technology. NVIDIA’s GPUs used to have a dominant position as the supplier of rig ICs, but now they are insignificant. The supply of mining rigs via the Chinese companies Bitmain and Canaan Creative covers north or 90% of the market. Trump’s policies had the effect of accelerating China’s project to in-source all this. And even without Trump, China has a long-term policy objective of freeing itself entirely of dependence on US/European tech. I.e., western democratic control of things.

So, if you trust in China, then crypto is your solution.

As an important coda, it should be mentioned that China is a totalitarian society which is openly inimical to western liberal democracy and, most of all, the west’s dominance of world financial systems. Some people argue that because of the aspects of PBFT and the game theoretic implications, there’s no way the mining operators or the rig suppliers would shoot themselves by undermining their businesses if the Chinese Communist Party ordered them to do it. Wrong and laughably naïve. Ask Jack Ma.