Daas Torah is a talmid chacham’s/a gadol’s opinion of how the Torah and Hashem would want you to act in a non halachic situation. However, this does not necessarily mean that they understand the situation completely accurately. While many Rabbonim felt that Daas Torah was to stay in Europe, it could have been based on the fact that they misunderstood how powerful Hitler and the Nazis were. If they had a better understanding of the situation they may have felt Daas Torah would be different. (Or, on the other side, it could be that they did understand how powerful the Nazis were, they were never claiming it’s safer to stay in Europe, they were just saying better to die frum in Europe than to survive and risk assimilation by traveling to America or Israel.)
And, there is not one Daas Torah, it’s an opinion and therefore subjective. R’ Kanievsky, R’ Shteinman, R’ Schacter, and R’ Lichtenstein’s assessment of how Hashem would want you to act in a given situation are all Daas Torah, even though they probably disagree with each other on many accounts. There could be a machlokes. Daas Torah is not objective and there is not one “posek” who determines what is Daas Torah for all of Klal Yisroel.