research the matter
I kinda agree with you. Maradona did make the interest in calcio grow.
What you failed to mention (or maybe you did and I missed it?) is that until the early 90's, there wasn't a strong TV coverage of foreign leagues. I talked about this matter with people from many countries actually. In Yugoslavia we were getting the Champions Cup and the big NT competitions, but the domestic league was quite strong so no-one was broadcasting foreign leagues. I realized that it was exactly the same in the other countries.
Sometimes around 1990, I believe it happened even a year or two later, the TV stations started buying the rights for foreign leagues so Europe could see week in week out Bundesliga, serie A, EPL and La Liga.
By that time Berlusconi made Milan a super power and forced the other Italians to start investing heavily. That's how the league became popular. It was the strongest when the broadcasting started.
So Maradona did make the league more popular, but it was mostly by people looking for articles in the papers to see how did Napoli do and if Maradona scored.