Alle (all), einige (some), mehrere (several), verschiedene (various), viele (many) and wenige (few), in addition to being used as pronouns, can stand in front of plural nouns with an adjective between the two. The endings required after alle are the same as for the plural of der/die/das and those required after the others are the same as for unpreceded adjectives, i.e. the ending on the pronouns is identical to the ending on the adjective, e.g.

Nominative:  alle guten Leute / viele gute Leute

Accusative: alle guten Leute / viele gute Leute

Genitive: aller guten Leute / vieler guter Leute

Dative: allen guten Leuten /vielen guten Leuten

The reason for this distinction in endings between alle and the other  pronouns is that alle refers to a definite number and the others to an  indefinite number.