Yup, that interest is paid towards shorts in 20mins. So a bunch of longs sold out at market order to take profit and avoid interest which in turn caused the snowball effect on further long liquidations.
Happens every single time like this when interest creep up to such higher percentages an hour before interest is due.
Odds are it was just a few individual traders with millions in open position who caused the bitmex ripple. Probably had couple of BTC due for interest that they avoided.