This sort of claim seems to run into historical problems

Athens lost to sparta. But it was a close call. Sparta excelled at nothing but war. Athens spread its efforts around and was good at everything. And it was close! That's how much more powerful Athens was: it did tons of other stuff and nearly won the war anyway.

If Athens had had an extra 100 years to improve, it would have gotten a big lead on Sparta. Long term, that kind of society wins.

A lot of major expansionist violent empires have done quite well for themselves.

Not long term.

Or to use a different, but potentially more controversial example, in North America and in Australia, the European colonizers won outright, despite having extremely violent, expansionist policies.

They were up against closed societies that were much worse than they themselves were in pretty much every respect including morally. The natives were not non-violent philosophers.