。
The people rebelled against their rulers.
Literal
People [topic-は] rulers [at/against-に] rebelled.
反抗する ('to resist, rebel') takes its target with に, not を — the thing rebelled against is the indirect recipient of the resistance. 支配者たち uses the plural suffix ~たち to mark 'rulers' as multiple people; without it, 支配者 could be singular or generic.