That is what I mean - when the stable coin getting unstable, bitcoin getting more stable, why this happening?
it is mostly a coincidence. bitcoin had a certain trend. look at 2013 till 2015 as a trend that is already over. the price shoot up to a bubble by the end of 2013 then the bubble burst and price came down. a bear market started and finally came to an end. in 2015 (end of bear market of that time) price became stable and that lasted a couple of months. Tether wasn't having troubles back then. it wasn't even that big.
same is now. it is the trend that bitcoin is on which made it stable. it is one of the stages! it has nothing to do with Tether.
Stable coin is a definition for one coin which can prevent people's asset from loss when something big or negative effect happens. I do not believe those coins like USDT will inherently be a stable coin, they were manipulated by a company, also it is not possible for any one company to support the world class stable coin volume.
From this perspective, I rather believe bitcoin will be a universally accepted stable coin in the world when it is getting acquainted by everyone on the earth.
that is not a wrong definition. but as i said price being stable doesn't make it a "stable-coin" because that term is usually used for certain coins like Tether which are pegged.