It gave archaeologists an opportunity to recover organic samples from within the hill and submit them to radio-carbon dating.
So what have we learned that's new? Not very much. We already had a rough idea of the date when construction started; that's now been narrowed down to 2,400 BC- give or take a generation. Atkinson's 1968 theory that the hill went up in three stages has been strengthened (or at least not disproved). And that's about it.
What was Silbury for? Nobody knows. A ritual platform, a solar observatory, an icon of the winter Goddess, a big, fat status symbol- they've all been proposed and none of them disproved. Silbury is a very "clean" site - which suggests ritual use and restricted access.The only hypothesis that's been conclusively ruled out by centuries of fruitless digging is everybody's first guess- that it's a tomb.
Oh, one genuinely new piece of information- They found a huge post-hole on the summit that dates to the11th century CE, also an armour piercing arrowhead. Put them together and it seems that the Saxons used the hill as the footings for a watchtower or fort.