800,000 Frontier Troops March on the Capital. Why Has the Emperor Rebelled?

Since ancient times, frontier troops have been elite forces, forbidden to enter the capital without an imperial decree. If you march on the capital with 800 frontier troops, the emperor considers you nothing more than a rabble not worth worrying about. With 8,000 troops, you're, at best, a band of marauders large enough to pose a modest threat. With 80,000 troops, you're a massive rebel army capable of shaking the foundations of the dynasty. But if you march on the capital with 800,000 frontier troops, then it isn't the soldiers who are rebelling. It's the emperor! Chen Chuyan's soul transmigrates into the Great Yu Dynasty, where he becomes a member of its frontier army and awakens the [Infinite Provisions] System. He earns one point per second, and can exchange points for silver and food. By then, the Great Yu Dynasty, with 279 years behind it, has long since passed its peak and entered a rotten, decrepit final era: Barbarian tribes invade from outside, with powerful enemies all around. Within the court, treacherous officials hold sway and the emperor is incompetent. The 800,000 Great Yu troops stationed at the nine frontier strongholds have had their provisions withheld and wages unpaid by the court for months. The soldiers have no decent clothes or enough to eat, while their families are displaced and destitute. Chen Chuyan, who has transmigrated into this world, uses the 86,400 points deposited into his account each day to buy money and provisions. The frontier soldiers finally have their fill of food, warm clothes, and their full wages. In five years, Chen Chuyan rises from a young officer guarding the northern frontier at Shuobei to become the commander-in-chief of the nine frontier strongholds, overseeing their military and civil affairs, as well as the Great Yu Dynasty's general tasked with pacifying the border and commander-in-chief of its troops. Just as internal turmoil breaks out and the frontier army receives an imperial order to march on the capital, its soldiers drape a yellow robe over Chen Chuyan's shoulders and, on behalf of the 800,000-strong army, demand to know why the current emperor is rebelling.