I believe there was a substantial urban population among the Samnites. Archeological research into the Samnites seems to have uncovered a network of relatively developed sites - more than a petty tribal confederation at any rate.
We can debate why Rome rose indefinitely, but we should be careful as some in this thread have done of attributing the rise of any ancient state or hegemony to a single factor. Generally why states and peoples succeed or fail in their ambitions is a complex and multifaceted science. I know that what I just said might be obvious but people seem to have jumped to some hasty conclusions. Rome's formula was not unique to them, and it changed a lot over their history.
Also I was unaware that the Achaemenids rise was due to luck more than every other event in human history is due to "luck."![]()
The Samnite heartland was probably less urbanized and less populated than Latium and the Roman hegemony (which, when the clash with Rome occurred, had come to include a significant portion of Southern Etruria, clearly the most advanced part of Italy outside Megale Hellas at that point). Also, the political modes of organization the Romans had developed were more centralized than anything the Samnites appear to have had. After all, Rome won.
OTOH, the demographic, organizational and technological imbalace that favored Rome was not that big (in terms of technology, the Samnites were probably about the same level; in terms of purely military organizations, they may have been even ahead of Rome initially). Note, however, that the Samnite urban tradition was younger than Latium's, and demography likely favored the Roman side as long as the Samnites had not stable control on any of the major fertile coastal plains (while Rome's core lands were precisely in one of these) - the entire Roman-Samnite conflict was largely started by the Samnite attempt to control such a plain (the Campanian one, where the older order dominated by the Etruscan elites and Campanian groups - the latter very close to the Samnites linguistically but not aligned to them politically - was falling apart). The core Samnite lands were in the less productive Appennine highlands - which however offered defensive advantages.