# Why connected Lie groups are homotopy equivalent to connected compact Lie groups?

I am looking for a simple proof of a Mostow Theroem, which asserts that any connected Lie group $G$ admits a maximal compact subgroup $K$ (which is necessarily connected) such that $$G\simeq K\times\mathbb{R}^d\quad(\text{for certain}\ d).$$ So $G$ and $K$ are homotopy equivalent, so they have exactly the same cohomology groups.

I wonder if there is a 'simple' proof of the above theorem.