Must read article about Polybius. You can read it here: https://engelsbergideas.com/essays/four-reasons-to-study-polybius-most-practical-of-ancient-historians/
I really love historical and philosophical debates about whether history is linear, circular, hegelian etc. and Polybius is one of my favorite circular historians. It just makes a lot of sense. The topic is only so interesting because there's truths to most view points - even great man theory!