Q: Why does a Typhoon drop a thousand pounder???????
A: Because it can!!!!!
Q: Why does a Typhoon not drop something smaller instead??????
A: Because it can't, as the smaller weapons haven't been cleared for release/carrage from the aircraft yet as it requires software changes, testing and quite a bit of money.
Plus if you look closely at that footage of the 1000 lb bomb hitting that tank, you will note there were another two tanks and an APC in very close proximty, which are most likely now not in anything like a good working order.