I think, from my knowledge of its historiography, another example of the political/ideological factor being crucial is in Nazi Germany (sorry if I can't provide examples more further back, I'm better versed in modern history really). Although the early (and often Marxist-oriented) historiography of Nazi Germany tended to be quite focused on social processes and the emergence of a robust German middle class as key to understanding Nazism, more recent historiography tends to focus on Nazism as an ideology and the brainchild of a single individual, Adolf Hitler (though his ideology had important precedents in German and Western intellectual thought). Nobody really thinks social processes were the root cause of Nazism anymore, and it's not nearly as popular an interpretation for the Soviet Union either (see Malia, Kotkin, Halfin). The same could be said on the historiography for the French Revolution (see Interpreting the French Revolution). In other words, in a variety of fields social history has fallen out of favour somewhat, and cultural/intellectual history is much more in vogue. I think this shows that historians are taking a more balanced approach to history and understand that political/ideological factors act as independent variables and are not always determined by supposed individual or group class interests.
Remember, Marx formulated his theories just when history as a proper discipline was emerging (correct me if I'm wrong), and since then social history and historical analysis has gone through many changes and improvements. In other words, there's no reason to take Marx as the most reliable source to judge the entirety of human history at all - and that's precisely what he did. Marx has to be viewed in context, as just another writer of his time with extremely brilliant (yet flawed) and consequential ideas. I don't think his views were so influential because they were necessarily correct, but because they seemed to offer a solution to the eternal problems of the human condition. Unfortunately this did have bloody consequences for the 20th century.