Promising the non-romans citizenship gains you popularity.
Popularity gains you support, but if the people can’t vote, it doesn’t help come election time. But if the people can fight, then you can win the election by force.
Now that you’re in power, why would you make good on your promise? There is no reward for upsetting the traditional power structure once you find yourself at the top.
Fight like an underdog to get there. Defend your spot like your life depends on it, because in Ancient Rome, death was always on the table.
Swings of power go back in forth. Whether today, or 2000 years ago, we see politicians and leaders use the same rhetoric. “Support me because I care about you.”