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/Le moins = The most/the least (Superlative with Adverbs in French)

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 (Superlative with Adjectives in French)

Hope that helps!