I have some trouble while reading a proof of a lemma in the book

<cite authors="Conrad, Brian; Gabber, Ofer; Prasad, Gopal">_Conrad, Brian; Gabber, Ofer; Prasad, Gopal_, [**Pseudo-reductive groups.**](http://dx.doi.org/10.1017/CBO9781316092439), New Mathematical Monographs 26. Cambridge: Cambridge University Press (ISBN 978-1-107-08723-1/hbk; 978-1-316-09243-9/ebook). xxiv, 665&nbsp;p. (2015). [ZBL1314.20037](https://zbmath.org/?q=an:1314.20037).</cite>

Here is the lemma:

> **Lemma C.4.4.** Let $G$ be a group scheme locally of finite type over a field $k$, $T$ is a maximal $k$-torus in $G$ and $K/k$ an extension field. If $G$ is smooth or commutative, or if $K/k$ is a separable extension, then $T_{K}$ is a maximal $K$-torus in $G_{K}$. 

In the proof, the authors wrote:

> Suppose $G$ is connected and commutative. Any $k_{s}$-torus in $G_{k_{s}}$ has a $\text{Gal}(k_{s}/k)$-orbit consisting of finitely many $k_{s}$-tori, so by commutativity the collectively generate a $\text{Gal}(k_{s}/k)$-stable $k_{s}$-subtorus.



I don't know why a Galois orbit of a $k_{s}$-torus has only finite tori, can anybody explain this for me? Thanks a lot. 

  


  [1]: https://i.sstatic.net/TFzE4.png