Earlier quoted context omitted.
The general public was often using Times New Roman or whatever their system's default sans serif font was. But, designers have cared about things like this for a very long time (ages, as you said.) Arial is joined at the hip with Helvetica, which got a movie[1] because of it's massive cultural impact and it's praise within design circles. Among professional designers, there were very strong opinions on Helvetica and…
Ah yeah I had totally forgotten about Helvetica having such a history. Though I wonder what you mean by putting Arial in that position deliberately - if it was alphabetical (which I remember it being) do you mean that Arial was named as such that it started with A?
From what I know, Monotype was responsible for the name Arial (although IBM called the family Sonoran Sans Serif.) But, even at that point, the intent was to create something that would stand in for Helvetica.
I don't know that the name was selected deliberately to be ahead of Helvetica. But, it's not unheard of in branding to put your product ahead of or near the competition alphabetically. (It was especially important then because people were manually looking up things in phone books and libraries.) I wouldn't be surprised to hear that aspect was considered during naming.