Anyone can tell you that a commodity cannot jump from $1000 to $19 000 in a couple of months without manipulation. So this should not even be news.
The Tether angle is new, so I would give you that.
Everyone seems to be looking for an explanation on why the price is dropping and why we do not have a great year, but the answer is right in front of you. Bitcoin is based on Supply & Demand, and the Supply has increased and the demand has decreased.
By an extension of your logic, no commodity can jump from a few cents to $1000 in a few years. Bitcoin has done just that. So would you conclude that the price rise during the initial years was manipulation too.
There may have been some manipulation during the price increase, but your logic that such a bull run is impossible without price manipulation is flawed.