Why is the number of components of Lie group finite?

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The following quote is from An Introduction to Lie Group and Lie Algebra by Alexander Kirillov. By "discrete" he means that $|G/G^0|$ is finite. However, according to Introduction to Smooth Manifolds by J. Lee, a topological manifold has countable (not finite in general) components. So, I'd like to know what condition makes lie group to have a finite components.

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