Connection between $\operatorname{Var}(M^n v)$ and largest eigenvalue of $M$

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In a proof I am trying to understand, the following is stated:

$ M$ is a non-random matrix with eigenvalues $\lambda_i$, $v$ is a random vector, $n$ is a scalar,

$\operatorname{Var}(M^n v) \ge \max(|\lambda_i|)^n $

As I copied this from the blackboard, I might have made a mistake. Our script says

$\ \lim_{n\to\infty}\operatorname{Var}(M^n v) = \infty \mbox{ if } \max(|\lambda_i|) > 1 $

(which would be implied by the first inequality).

If anyone could explain why this holds, or point me to a paper/book where this is explained I would very much appreciate it.