Not necessarily. I don't believe Tether has the backing they claim. Given that though, the subpoena wasn't public yet and it is plausible clients may have been continuing to send Tether money during that time.

This is what I thought about too. So either they just thought screw it, let's make hay while the sun shines, the feds will never get us - or they are legit

I'm not sure the US govt has any direct jurisdiction to stop them. And the investors receiving the USDT probably weren't aware of the subpoena.