There weren't any people actually living on the island of Krakatau itself, even before it started showing signs of unrest. The people who were affected were those on the nearby coastlines of Sumatra and Java, and for the most part, no, they were not prepared. Most of the fatalities occurred because of tsunami that were generated by the eruption, and these tsunami swept against the coasts of Sumatra and Java, killing around 36,000 people.

 

Also, people around the whole world were affected as the global climate was affected by the eruption.