Hi Varsha,
In this case the superlative "le plus" is modifying the verb "admirer", and adverbs have no gender so they always use the masculine form:
Le plus and le moins = the most and the least (superlative of adverbs)
However, if it were modifying a noun then you would agree with the gender:
Le, la, les plus and le, la, les moins = the most and the least (superlatives of adjectives)
Hope that helps!