The article is quite kind to Schliemann. Kinder than many archaeological experts.

The excavated area thought to be "Troy" had about nine distinct layers. The "Troy" that everyone is interested was one of the upper layers (like Layer VIII, the second from the top), which Schliemann kept digging through. The one he finally settled on and brought "Priam's Treasure" from was much older, long before the era of the fabled Trojan war.

To boot, with each successive layer, the previous layer he simply dumped to the side and didn't take much care in preserving. So much of the Trojan layer that the classicists are interested in studying has actually been destroyed by his attempts to dig deeper.