From their website : "As Stablegains is not a traditional US bank, the funds are not secured by the FDIC. While we aim to make every effort to understand and mitigate everything that can possibly go wrong, there is still a non-zero risk you can lose your deposit. Our advice is to diversify and never invest all of your savings in a single place."
Of course they are selling themselves as pretty safe, and I'm sure they thought they were. But as you mention, it's like the 10th stablecoin to drop, so it's not exactly a surprise that crypto is a risky investment in any case.