star trek - What was the entity looking for that took Voyager into the Delta quadrant?

The "Caretaker" was looking for beings capable of maintaining the array that was caring for the Ocampa.

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The Caretaker reveals that he was part of an alien race whose technology had long ago accidentally caused the rainfall cycle on the Ocampa planet to become disrupted and leaving it arid, due to the destruction of that particular M-class planet's atmospheric nucleogenics. To make up for the error, he and another of his race stayed behind to care for the Ocampa. His companion having long moved on, the Caretaker has used the Array to seek species from distant galactic sectors with the potential to help him reproduce and maintain the array; the strange disease that Kim and Torres had was a result of that test.