"... Contrary to popular belief, Queen Chrysalis is not the ruler of all of Changelingkind; although she herself makes this pretentious claim as part of her long list of titles, she is merely one of the countless pretenders to that title.
Politically, the Changeling race is currently experiencing a period that could be best described as a "Warring States" era, similar to those of in the history of the Neighponese and Qilinese Empires in the East: A unified Changeling nation, a polydomous hive known as the Grand Empire of the Changelings, once existed in the distant past for over a thousand years, founded by Rhyniognatha the Conqueror, the first Changeling King, who ruled the Changelings from the Throne of Horns in his hive palace, along with his descendants.
However, centuries of court corruption and crown negligence, dynastic power-struggles, and an escalating series of crises in the form of consecutive famines, natural disasters and increasing monster attacks, led to the gradual weakening of the once powerful ruling king/queen and central government, and increase autonomy of the Changeling nobility ruling domains in the monarch's name. When the last supreme changeling queen and her royal family were assassinated three centuries ago, the Grand Empire disintegrated and fragmented into hundreds of smaller hives and colonies.
Controlling these splintered territories are rival Drone Lords and Brood Matrons who claimed the title of Kings and Queens, and fought for control of the Changeling lands, each claiming to be the legitimate inheritor of the throne and ruler of all of Changelingkind. The Changeling lands, once fertile, had been reduced to ruined badlands by three centuries of constant warfare and dark magic, filled with demolished hives, infested with wild beasts and bandits, and strewn the rotting carapace remains of dead Changelings, whether fallen warrior or massacred innocents.
The intercene conflict had been the cause of considerable suffering of the Changeling people for countless generations, but their plight are generally ignored by the Changeling warlords; being born to war and rule with absolute power over their subjects, each Drone Lord or Brood Matron are, as a whole, vain, ambitious, ruthless and deprave beyond common sanity. All are driven by intense literal and metaphoric hunger for power over others, a goal they continue to pursuit with monomaniacal determination at the expense of everyone and everything else.
While the greater Changeling warlords continue to fight and scheme among themselves for supremacy, lesser warlords, such as the relatively young and ambitious Queen Chrysalis, unable to wrest control of greater warlords' domains and risk conquest by them in turn, often expand outwards to conquer new territories and subjugate other races, both to expand their power and bring new harvest of cattle love into the Changeling lands. Many smaller hives, breeds and colonies, desperately trying to escape fighting, oppression and extermination by stronger hives, fled to all corners of the world in what would become known as the Changeling diaspora, establishing Changeling communities, both peaceful or malicious, among many kingdoms of the world in secret.
As of today, no self-proclaimed Changeling King and Queen have yet prevail over all other rivals, and that is not likely to change in the foreseeable future with the current state of affairs in the Changeling badlands. Until a Changeling warlord whose strength and cunning could rival Rhyniognatha himself emerges to wipe out all other rivals, the Throne of Horns shall remain empty..."
--- Extract from the Codex Equestria entry of the Changelings, Edition III, Chapter IV, Section 8: Changeling Politics.
A horrible accident while she was working as an intern at a small office in Manehatten, involving an industrial 3-hole punch. It's only mentioned briefly in a flashback, but the fan theory is that that event is what turned her to evil.
You're being way too nice, and making me feel bad for lying to you.
The swiss-cheesiness of changelings is never addressed in the show. I suppose they just did it because it looks visually interesting, and it helps to further differentiate the changelings from ponies, making them more stranger and more foreign. I like my version better though.