The soviet union collected data and profiled American citizens so that they could (potentially) be used as dumb pawns if needed. Dumb pawns that didn't even know that they were doing the bidding of the soviet union.

Just like how Kim Jong Un killed his brother using dumb pawns to actually carry out the murder.

So if your head has not grasped this reality, then they are already two steps ahead of your "What could they possibly do".

This is also the reason why congress keeps banning Chinese enterprise. It's not because they care about privacy, it's because they care about people being turned into pawns.