While Lemkin himself cites the Armenians as a basis for the word "genocide," the historiography of an "Armenian Genocide" only came in the late 1970s, as 2nd generation Armenian-American historians began to think their past comparatively.
https://books.google.com/ngrams/graph?content=%22Armenian+Genocide%22&year_start=1948&year_end=2019&corpus=26&smoothing=3

There is a broader historiographic context here: "Holocaust Studies" really only begins in the late 1960s and early 1970s and the first, landmark histories of the Holocaust date from the early and mid 1970s.

Early historiography of the Armenian Genocide were, in part, a response to this. Particularly in the 1990s, "Holocaust Studies" fell out of favor and was replaced with "Genocide Studies," which was, in general, more comparative and looked at a far wider set of cases

The much shared video of Bernard Lewis, in my view, is a historiographical artifact, clearly responding to an earlier literature that has largely been by-passed by later scholarly debates