How FWRA/FWIA has such high volume despite being so small?

I was comparing the trading volume of some World ETFs from last Friday:

Invesco FTSE All-World - FWRA (Milan): 77.45K - FWIA (Frank.): 208.71K

SPDR MSCI All-Country World - ACWE (Milan): 6.17K - SPYY (Frank.): 37.84K

The weird thing is that FWRA/FWIA has 1.1bil AUM, whereas ACWE/SPYY has 4.6bil AUM. How is it possible an ETF that is over 4x smaller has such higher trading volume?