The weapons used were apparently arrows and wooden clubs, so how is it they call this a “Bronze Age” battle site?
Because the Bronze Age in Europe spanned (approx.) the years 3000-600 BC.
1. "Bronze Age" is a dating method.
2. Bronze weapons may have been valuable enough that they were not left behind by the victors. Looting the bodies of dead enemies is a longstanding tradition of war.
3. Bronze Age just means that bronze was smelted and used for some tools/weapons. Not that it was common or inexpensive.
That’s just the stuff they left behind. :’) But your question points to what I regard as the fundamental stupidity of continued use of “bronze age” “iron age” etc to date things.
It is also unlikely that there’d be a lot of bronze left on the battle field. It was valuable.