If you can't read the Y-axis on a graph, and you only look at the last 7 days, then it looks like Tether has gone off a cliff.
If you read the Y-axis you'll see it's barely moved, and if you zoom the graph out, it's barely a blip compared to previous deviations in price.
Now it may well be that Tether is also heading to zero, but it's very different from the Terra fluctuations.
Check the following graphs for both 7 days and all time