And the remains of the Krakatoa island that are bracketing the new volcano channeled the wave?
From the photos (above) it does appear that the southwest quadrant of the volcano collapsed, yet the deadliest waves it Lampung to the north and Sumur to the southeast.
My grandchildren are on school holiday, and I had booked a bungalow at our usual beach digs in Anyer for Thursday 27/12. I thought we really dodged a bullet, but yesterday I rang them up and the lady at the resort told me they suffered minimal damage. The main problem is that the road to there is jammed up and damaged.
It may be assumed that Pulau Krakatau Kecil blocked the main wave from moving to the northeast with deadly force. Note further that Carita and Sumur were more badly damaged than was Tanjung Lesung, which had Pulau Krakatau between it and Anak Krakatau.