I do wonder though at this time of international tension whether the Poles should be risking valuable aircraft and pilots with stunts like this.
As a (naturalised) Polish citizen, I can safely say that I think that using F-16s for air shows was nothing short of pure stupidity. It's the classic post-communist thinking, where you have to show off the best equipment rather than using something cheap and simple. They've now been removed from air shows, but I still cannot work out why they were being used in the first place. In general, the Polish Air Force has a poor reputation for safety, and a friend who flies a fairly large amount of flights on a small passenger jet constantly complains about the military forcing sudden and unexpected changes when in the air.
Radom Airport has sustained considerable damage too, and it will be closed for at least several weeks to repair the damage.
I've seen online suggestions that he didn't realise he was too low at the top of the loop so didn't have the altitude to pull out of the dive, very similar to the accident at Shoreham. Also he may have blacked out due to excessive G-force when trying to pull out.
It was almost certainly pilot error, but also a huge organisational error in allowing these planes to come so close to the ground in the first place. There are plenty of comments that it was the norm for them to fly within tens of meters of the ground at air shows, which simply shouldn't be happening.