Loyalists during the American Revolution weren't a homogenous group, but a collection of various ethnicities with a wide range of beliefs and motivations. Many were devoted to the Crown and feared that rebellion would lead to disaster. Many of those considered as Loyalists or "Tories" also agreed with the rebels that there were real issues Britain needed to address in America, but felt that any grievances between the colonists and Britain could be handled internally within the Empire. Loyalists would often face persecution, loss of civil liberties, violence from Patriot mobs and confiscation of property, if their allegiances were made public. Very few were wealthy, as most were tradespeople and farmers from the lower classes who had lost everything during the war.

Others sided with Britain because they were recent immigrants, or linguistic and religious minorities who didn't fully integrate and weren't accepted in colonial America; or, those on the periphery of American society, such as blacks and native peoples, who were enticed with promises of freedom or a native homeland. Close to 19,000 Loyalists fought in provincial militia corps during the war, including units formed by ex-slaves who won their freedom by taking up arms for Britain. Other Loyalists stayed in British-held strongholds like New York City and Boston as the war continued.

After Yorktown, 80,000 - 100,000 Loyalists left America. Some departed for various British colonies in the West Indies, or back to Britain. Half would settle in Canada, including the Maritime colonies (where most of them went from 1783-84), and in what we now know as Ontario and Quebec. These Loyalists were eligible for compensation and offered land grants for their past service to the Crown. Free blacks, former slaves and native peoples who fought in Loyalist corps also received land.

A subset of later migrants from America, known as "late Loyalists", moved to Canada in the 1790's more for economic reasons and offers of cheap land than for love for the Crown. Most of these moved to sparsely populated Upper Canada (Ontario).

The influx of Loyalists would later help to shape a burgeoning Canadian identity and, some 80 years later, create a country of their own.

EDIT: There were wealthy Loyalists who had formed the political and business elites before the war. After the war, some returned to Britain, as they had the financial means or business and political connections to do so. But the vast majority of Loyalists were ordinary people of lower social rank and limited resources, ostracized and driven out by their Patriot neighbours. These had little choice but to leave.

It's estimated that up to 20% of the white population in the 13 Colonies at the start of the revolution were Loyalists. Those that didn't or chose not to leave for Canada, Britain or other colonies remained in the US due to familial or business ties, held property or had sufficient social standing in their communities.