Not because he wanted it so, but because he had no choice.
5 seconds sound clip from the Alexander the Great (1956) movie soundboard.
You can hear this line at 00:31:33 in the Blu-ray version of the movie.
Quote context
[...]
- He is, in his single person, lord of all things, both open and secret, at once general and absolute.
- I am leaving Antipater here as your adviser.
- Alexander, there's another ancient law of kingship: to trust no one, and to learn how to be alone.
- No.
- Not because he wanted it so, but because he had no choice.
- Alexander, I swear to you...
- Who else should I have fought for except you? What other love do I have?
[...]