Complex sentence: Kokkinokremos was a short-lived settlement, where the presence of various caches concealed by smiths suggests that none ever returned to reclaim the treasures, suggesting they were killed or enslaved.
Split into simpler sentences: Kokkinokremos was a short-lived settlement, where various caches concealed by smiths have been found. That none ever returned to reclaim the treasures suggests they were killed or enslaved.