Let us see, how vyAsa described the 4 caste maintenance by Dushyanta:
Vol. 1 Adi Parva. Chapter 062. Verse 006. Dushyanta's Administration
sa bhuGktE ripumardanah-
na pApakrit kaS cid AsIt
tasmin rAjani SAsati
kAlavarshI ca parjanyah
sasyAni phalavanti ca-
mahI vasumatI tadA
CONTEXT AND GIST
Sage VaisampAyana was describing Dushyanta's rule. He had taken one whole chapter of 14 verses to give introductory description of D's rule following which he was asked to narrate the full story.
Gist: Dushyanta subdued even barbarous tribes and mlEchchas (invading aliens). He had his sway on lands upto the four seas, filled with persons of four castes.
There was no mixing up of castes (varNa sankaram). There was no tilling for agriculture. There was no mining for minerals. (Ganguli's comment: Even without tilling fields were prospering. Everything was available on the surface. There was no need of mining.).
There were no sinners.
Rain God Parjanya (Indra) showered rains abundantly and harvests were bounteous.
The Earth was full of gems and precious stones.
There can't be much difference between modern paid biographers and ghostwriters and the ancient chroniclers. Every newspaper and every TV channel cry hoarse about paid news. Yet, they produce paid news only.
Did the Rain God Indra (Parjanya) have time to shower rains? He must have been busy stealing sacrificial horses. He must have been busy with Urvasi, Rambha, Menaka and Tilottama.
What was Dushyanta's secret? How he was able to prevail over Indra?