Secondly and most importantly, bitcoin is something that goes up when people buy more bitcoin than they sell it, there is literally NOTHING else that would make it go up, this is not a company, this is not a stock or share, this is bitcoin and the price only changes depending on how people trade it and that's it.
The same thing applies to
any investment asset, including stocks. Stocks have a limited number of shares issued so they are ruled by supply and demand, just the same as Bitcoin.
This means if dollar gains value or loses value is irrelevant
Personally I am skeptical of a concrete causal connection, but it's definitely possible. There is lots of capital tied up in dollar-denominated debt and bonds. As yields drop, it only makes sense that those investors exit for markets with better returns, meaning risk assets like stocks, BTC, and gold.