According to my humble opinion, there are 3 reasons that lead to the current Bitcoin Bull Run:
1/ US Stock market: the US stock market has experienced strong growth over the past few years and may now be at the peak and unpredictable, the complicated trade war between US and China is confusing many investors, investors are even more uncertain about the long-term stability of stocks, so they are thinking about the other profitable investment tool, which is crypto and in the short term - Bitcoin, bitcoin is now widely known, it also has a US stock market derivative tool, bitcoin's inflation percentage also falls cyclical and more importantly its expected interest rate for a long time is quite attractive for adventurous investors, those factors will create interests for America investors in investing BTC.
2/ Miners: we all know that Bitcoin halving is very near (less than 1 year) and roughly 17 mil bitcoins have been mined. This made the demand of BTC increased. One other reason is some big mining company is preparing for US IPO (i.e. Canaan Creative), so they need to keep the BTC price high, then they can sell more mining device
3/ The need of USDT from Chinese: Since China government is issuing strict capital control measure and also weaken their currency. Therefore, USDT is a very good way for Chinese investors to escape this situation. This added more power for this BTC run.
No i don't think so. The Chinese don't need USDT or any of the others, they are using Bitcoin and perhaps some few other altcoins if only to bypass controls. The Chinese Yuan is currently very strong against the USD (let alone USDT with its "30%" fractional reserve).
Canaan big? Well i guess Bitmain was trying to IPO closer to their home but Jihan Wu went crazy pursuing unneeded things like an altcoin, but who knows with the new guy if they will try again. But i doubt that has anything to do with it.
Your first comment sounds more reasonable. The traditional (flee to) when things look bad are metals, but some investors might be combining with crypto.
I doubt this has really much to do with the "bull run", i think its just the halving expectancy, and nothing more. We had already one and corrected, this might be too early and could go back down again before finally going for the halving run.