Motilal Osawal NASDAQ 100 ETF and FOF

Motilal Oswal has one ETF anf one FOF(fund of funds) that invest in NASDAQ 100 index namely
Motilal Oswal NASDAQ 100 ETF
Motilal Oswal NASDAQ 100 FOF

The FOF basically buys the Motilal Oswal NADSAQ 100 ETF

The expense ratio of ETF says 0.54%
But the expense ratio of FOF is 0.1%(direct) and 0.5%(regular)

Why is the FOF expense ratio less than the ETF. Or does it indicate that the FOF has an additional expense over the ETF. (i.e for direct 0.63946% (100-((100-0.54)*(100-0.001)))

Then doesn’t it simply make sense to buy the ETF. What is the benefit of buying FOF?

FOF expense ratio is .54+.1 = . .64
FOF easy to buy from amc website, SIP is possible.

FOF expense ratio is the underlying ETF expense ratio plus the expense ratio of the FOF wrapper.