Complex sentence: All typical objects in aphelion would seemingly approach closely to Jupiter, which should be destabilising for them--but the variation of the orbital elements over time prevents this, and conjunctions with Jupiter occur only near the perihelion of Hilda asteroids.
Split into simpler sentences: All typical objects in aphelion would seemingly approach closely to Jupiter, which should be destabilising for them. But the adjustment of orbital elements over time helps to avoid this, and conjunctions with Jupiter occur only near the perihelion of Hilda asteroids.