Learn Polish: Osiem kobiet zorganizowało tę kampanię. - Eight women organized this campaign.

This is the core rule for numbers 5 and above! When the subject involves a number like osiem (eight), Polish treats the whole phrase as a single, neuter quantity. Because of this, past tense verbs must take the 3rd-person singular neuter ending -ło, as if you were saying "an eight of women organized it."

Why is the noun kobiet used instead of the nominative plural kobiety?

In Polish, numbers from 5 upwards require the noun that follows them to be in the genitive plural case. The grammar works a bit like saying "an eight of women" to express quantity. The genitive plural of kobieta is kobiet.

Why does the sentence use tę instead of tą?

The campaign is the direct object receiving the action, so it takes the accusative case (kampanię). The correct feminine accusative form of the word for "this" (ta) is tę. You will often hear native Polish speakers say tą kampanię in casual, everyday speech, but tę is the strictly correct form for writing.

What aspect is zorganizowało, and what is its base verb?

It is perfective. The base imperfective verb is organizować (to organize or to be organizing). Adding the prefix z- creates the perfective verb zorganizować, which emphasizes that the action was successfully completed: they finished organizing the campaign.