Does that mean Sarmatians were neither united, nor charismatic nor prosperous?
Ancient Europeans (ie Sarmatians, ie in original- Serbs) were not united. They were aware of itself- in sense that one who was born on Pictish islands knew that he can walk all the way to the Black Lake (Black Sea) and walk thru the land of his brethren, thru Sarmatain realm. But, ancients were not united. At least, there are no historical records of it.
But we know of similarities in Slavic (ie Baltic, ie Sarmatian) pantheon and deities. If deities were similar and same it is quite logical that ancients spread their culture, for sure peacefully but also we can presume that some martial and unifying authority, at some point of time, existed and took part in spreading and supported `global` religious concept.
Charismatic? Yes, some for sure were charismatic but, or they were not charismatic enough or it didn`t help them.
Imagine prosperous Sarmatian leader in situation when there was no unity among Sarmatians and Greeks and Romans systematically sought to destroy all urban Sarmatian centers: in Thracia (Bylazora), in Anatolia (Troia), on British islands (Sorbiodunum), in Dacia (Sarmizegetusa), on Peloponnese (Sparta), in Etruria or as they called themselves Rasna (Sabatia and Perusia), in Gaul (Samarobriva), etc, etc. Urban centers were destroyed, rural population too often leaderless- object of hunt, slavery, loathing, relocation, assimilation and extermination. Religious elite (druids) were especially hunted and destroyed. Many local rural lords were subjugated with bribery. Some local rulers turned to hunt its own people in order to sell it to Greeks or Romans. Etc, etc.
But yes, we can only imagine how world of ancients looked like prior to Greeks or Romans appeared on historical scene. It was magnificent, I am sure. Worthy of books of one Tolkien. To create civilization relied on solstice and Sun as ultimate ideal, from British islands, via Danube, all the way to Baltic and Black Lake (Sea), via Anatolia and all the way all to the Ind River in one moment of time. It was surely magnificent. I am sure that ancients sow some form of unity in one point of their most glorious ancient era. Some Empire probably existed or maybe some ancient nomadic tribe ventured and dominated over others- nomadic also and sedentary. Some `Era of ancient Sarmatian kingdoms` of untold European and world past, sound fine to me.