[DVO]

You have the nuts, something like Ad 8d.

He has 78s, not diamonds. He hit the straight on the turn but your re raise now has him worried. He still called because a set is more likely and he wants to re evaluate on the river.

Any bet from you on the river and he folds.

There are lots of other hands you both play this way but I'll go with this.

I don't think he has the nut flush. He would 4-bet that to get full value from your hand with one card to go.

I'm prepared to be very wrong here. Interesting hand.