I agree tether looks dodgy - BUT - if tether was the only reason for bitcoin buys, bitcoin would still be in the $20,000 range.
The tether ecosystem might collapse, but as long as there are real bitcoin buys in dollars, euros, korean won etc, I don't think it will affect bitcoin too much.
You will soon learn how dodgy tether is from my 20min long documentary, i have been working on it for 6 weeks now. Soon everybody will learn.