Switzerland's currency is quite strong and considered a safe heaven. Do you think Switzerland has the capability or would invade another country to collected tax from a few billion people?
I am not an expert in how currencies work, but it's worth nothing that Switzerland, like most countries, keeps most of it's own reserves in USD (presumably treasury bills), and has around 1 trillion in USD in reserve. Which is not unrelated to the value of it's own currency and their ability to stabilize it. But I am not claiming to be able to explain the details myself.
That number you're looking at is "total Swiss foreign currency reserves in units of USD" not "Swiss foreign currency reserves that are USD". Switzerland, for reasons that are fairly obvious, holds large Euro reserves. At the end of 2020 USD was only ~35% of that total amount.
https://www.ceicdata.com/en/switzerland/official-reserve-ass...