We highly suggest that you take a read of this first.
In an exchange with a fan on Instagram (via comment section), Austin Carlile revealed one* of the reasons why he left Of Mice & Men.
*That one reason – they [Of Mice & Men] weren’t going to let Carlile write what he wanted on the band’s next (new) album – see photo below as evidence.
*Don’t worry Austin, you’ve got this! Keep calm and everything will fall into place!*