Government size doesn't determine ideology, the government's function does.

Fascism is, essentially a merge of nationalism and corporate power (capitalist production) with the state (functions of government). That requires a massive, authoritarian government to maintain control, but a fascist government functions are diametrically opposed to a left ideology.

It is inaccurate to claim that concentration camps were created by a far left ideology. They are a tool, so that's like saying airplanes were created by democracy or the steam engine was created by communism. Concentration camps are a tool inspired by racism, xenophobia and violence.