|Emperor Augustin Iturbide|
A junta was created that chose Iturbide as one of the regents of Mexico until a suitable emperor could be found. Iturbide's ascendancy to imperial power was largely his own idea. Iturbide ordered his troops out into the streets to demonstrate on his behalf. Following this peer pressure, this "spontaneous" demonstration on Iturbide's behalf was joined by other soldiers, and finally by civilians, all chanting the name of the August Emperor Agustin, much like how French soldier chanted "Vive l'emperor" just a few years earlier at Austerlitz. The mob demanded that Iturbide become emperor, to which Iturbide "reluctantly" (haha) accepted.
What was the process that made it happen? Mob mentality, egotism, and cheap theatrics.
Such is the process by which empires are built.
But how do empires fall?