Actually, there isn't much explanation here for why they were unable to accurately predict this tsunami, resulting in issuance of conflicting warnings, only that it happened.
Dozens of earthquakes rocked the region, but a tsunami didn't seem imminent. Then the massive waves began crashing in.
On Friday, a powerful 7.5-magnitude earthquake shook the Indonesian island of Sulawesi, just after 5:02 PM Western Indonesian Time. Dramatic videos revealed the eerie growth of a mounting wave in a bay near Palu, eventually crashing into the coast, causing onlookers to scatter.
Scientists were surprised by the ensuing tsunami, which resulted in conflicting warning messages. But experts suggest that the area's unique geology could be to blame for the unusual progression of the disaster. ...
The earthquake followed a series of temblors that began around 2:00 PM WIB with a 6.1-magnitude quake. That event not only destroyed dozens of houses but resulted in one death and at least 10 injuries, according to Reuters. The ground continued to roil with 27 aftershocks that eventually gave way to the intense, shallow 7.5-magnitude temblor centered about 6 miles deep, according to the U.S. Geological Survey. Since then, 31 aftershocks have gripped the island, according to CNN Indonesia. ...
Indonesian Agency for Meteorology, Climatology and Geophysics (BMKG) initially issued a tsunami warning but soon retracted it based on analyses at the time. However, monstrous waves soon began crashing on shore, captured in videos that quickly began circulating on social media. One particular video seems to be recorded from the upper floors of the circular parking structure at the Palu Grand Mall, showing waves rushing in below. It cuts off as the crowd starts to run, seeking safety from the wall of water. ...
https://www.nationalgeographic.com/environment/2018/09/indonesia-tsunami-sulawesi-explained-science-geology/
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