Th early solar system was very different with way more debris including large planetismals. The planetismals caused the big impacts you mentioned, and the small

Th early solar system was very different with way more debris including large planetismals. The planetismals caused the big impacts you mentioned, and the smaller stuff caused the impacts can see on other bodies. The solar system is much cleaner place now. All the planetismals and most of the asteroids have impacted or been kicked out. Big things are in stable orbits. There are a lot of dangerous asteroids but we track most of the large ones. There is a risk that something big will be kicked out of orbit but it is rare enough we don’t know how unlikely. Large impacts, 5km or bigger, are every 20 million years.