Why were federal and state debts so high?

America's growing debt is the result of simple math each year, there is a mismatch between spending and revenues. When the federal government spends more than it takes in, we have to borrow money to cover that annual deficit. And each year’s deficit adds to our growing national debt.

food chain i would say only because there is competition on getting food and survival

an interest group is an organization whose members share common concerns, and try to influence government policies that impact those concerns. elected officials frequently complain about the influence of "special interests" on american politics.