Why did the Huns, leaving Mongolia in the 1st c, reach the Black Sea only in the 4th c, while the Turks spent several years on this path?

The Huns’ movement in the 1st century was a flight from the Chinese troops. Having reached the Southern Urals, they stopped to rest and lived there until the middle of the 4th century, until the drought ended in the steppe and the Huns again intensified, united with other tribes. The movement of the Turks was an offensive by the troops of a prosperous nomadic power.