A thought popped into my head and I did about 5 minutes of research on this. I'm open to feedback, so feel free to criticize my post.
A quick Google search shows that the first gold ETF was launched around 2003. And below is a chart showing the price history of gold according to goldprice.com.
https://preview.redd.it/5pogd0qli0ab1.png?width=752&format=png&auto=webp&v=enabled&s=86093cdf81cf7f49559bf28642619f400f07e7e4
Correlation, not necessarily causality
Gold and Bitcoin are dissimilar commodities.
Take this graph and condense it to 5-10 years.
I’ve done the same research, OP.
Correlation doesn’t equate Causality. But sometimes it does.
We can’t ignore the amount of liquidity which began flowing into Gold via the spot ETF. In fact, some rabbit hole googling will get you numerous articles from the time naming the ETF as one of the main drivers of price action (the others being mostly an inflation hedge).
Think about how an investor could shift assets into gold. They had to buy physical gold coins or bars, usually at a markup. They then had to store those coins/bars, and then haul them to a buyer when they wanted to liquidate. The Gold spot ETF allowed them to gain exposure through their regular brokerage account and/or 401k. The similarities are too great to be ignored.