El Reg needs to do some primary school arithmetic ... from the article it takes 6 seconds to start an emergency generator (presumably of limited capacity).
So the lines fall over - bad luck for the people at the end but the system stayed up.
-7s three wind farms drop out -123MW
-0.9s two wind farms drop out -192MW
-0.5s interconnect hits 850MW (built for 600MW) and
-0.2s interconnect cuts out
So in 6.5s 315MW of wind power drops out and the interconnect overloads by 250MW and cuts ...
I.e. in the minimum time window there is a drop of 315MW of wind generated power, and the interconnector that until that time had been balancing with about 65MW spare capacity surges to 250MW over design and cuts out.
Until the wind farms dropped out all was fine, despite storm damage.