The Lubavitcher Rebbe in Likkutei Sichos (vol. 11, p. 74) quotes the Zohar in saying that if Yisro did not bless G-d and proclaim that G-d is the True One and Only G-d, the Torah wouldn't been given to B'nei Yisrael. As Deuteronomy pointed out in the comment-section, it was a triggering-event, Yisro blessing G-d was the trigger that made Matan Torah happen.
The Zohar says:
Came Yitro, illustrious High Priest, a master of all other deities, and praised the Holy One Blessed Be He, and said: "Now I know that Hashem is the greatest of all the other gods!". It was then that the Holy One Blessed Be He went up and was made known in His greatness on high and below, and then the Torah was given in its entirety, that it may reign over all.
There are several sources that describe the greatness of Yisro and the fact that he converted to Judaism. See for example the Or HaChaim, Rashi (the fact that Yisro went to the midbar for studying Torah) and the Rebbe in explaining why the Torah stresses that he once was a Kohen of Midian..
The Lubavitcher Rebbe begins to explain that when Yisro blessed G-d and said "Now I know that the Lord is greater than all gods", this caused:
“G‑d to be revealed in His glory in the higher realms and in the lower realms. Afterwards, He gave the Torah in its fullness.”
See the Rambam in Hilchos Avodas Kochavim who explain that anyone who denies the worship of false gods, acknowledges the entire Torah in its totality
This means, explains the Rebbe, that when Yisro studied Torah, that brought refinement of the unholiness and transformed it to holiness.
I find this explanation difficult to understand. Maybe because of the kabbalistic view of it. Therefore, I would like to know if there are any other explanations, non-kabbalistic, that explain the great virtue of Yisro (besides the fact that he recognised Hashem and converted, despite coming from a status of "Kohen Midian") and because of that, it was possible for the Torah be given.