~Snipped
Why? The simplest answer to that question is because it has more community support.
I might not have an exact answer for this but I have a theory. From a developer standpoint, Its better to create products and projects like stablecoins on a network like ETH since it comes with certain benefits. I know Ethereum blockchain has its own pitfalls but it does excels because it has more developer support, tools, SDKs, etc all powered by the community. It might be easy to spun a project from any blockchain but it takes more to maintain it especially on a blockchain without much developer/community support.