Why that one is the biggest? it just an options trading, it's an another "ETFs" thing that being approved by SEC.
It's hard to say which one is the biggest, and if we want to compare, we have to do many things for a reasonable comparison.
Price impacts of news in comparison.
Other factors, events that happened during a same period of the main news.
The first part is easy to do, collect prices and compare them, but the second part is more complicated, with many things we can include and also many things that can be important, but we can miss.
I recall that in a previous market cycle, news like "Bitcoin legal tender" and "Bitcoin beach/ city" in El Salvador, Elon Musk invested in Bitcoin, Tesla accept Bitcoin as a payment method, made more price impacts than Bitcoin Spot ETFs in late 2023 (rumor) and actual approvals in January 2024.
Additionally we have to consider that with bigger market cap of Bitcoin, price impacts from any big news will become smaller than in earlier market cycles with smaller market cap.