SB 4.13.11

matvā taṁ jaḍam unmattaṁ
 kula-vṛddhāḥ samantriṇaḥ
vatsaraṁ bhūpatiṁ cakrur
 yavīyāṁsaṁ bhrameḥ sutam
Word for word: 
matvā — thinking; tam — Utkala; jaḍam — without intelligence; unmattam — mad; kula-vṛddhāḥ — the elderly members of the family; samantriṇaḥ — with the ministers; vatsaram — Vatsara; bhū-patim — ruler of the world; cakruḥ — they made; yavīyāṁsam — younger; bhrameḥ — of Bhrami; sutam — son.
Translation: 
For this reason the ministers and all the elderly members of the family thought Utkala to be without intelligence and, in fact, mad. Thus his younger brother, named Vatsara, the son of Bhrami, was elevated to the royal throne, and he became king of the world.
Purport: 

It appears that although there was monarchy, it was not at all an autocracy. There were senior family members and ministers who could make changes and elect the proper person to the throne, although the throne could be occupied only by the royal family. In modern days also, wherever there is monarchy, sometimes the ministers and elderly members of the family select one member from the royal family to occupy the throne in preference to another.