they ruled is a past perfect tense
Revision:
In Past Perfect tense the verb is always preceded by "had"
I had ruled
you had ruled
he/she/it had ruled
we had ruled
you had ruled
they had ruled
Existed is the past tense. The past perfect tense is had existed.
The past tense is bled, and the past perfect tense is had bled.
The past tense of sit is sat; the past perfect tense is had sat.
The past perfect tense of hope is had hoped.
The past perfect tense is had set.
The past perfect tense is had submitted.
The past perfect tense is "had confronted".
The past perfect tense is had rung.
The past perfect tense is had burned.
The past perfect tense is had chosen.
The past perfect tense of "learn" is "had learned."
The past perfect tense is had bathed.