“Initially Lisa Page and Peter Strzok also transferred to the Mueller team; but they had to be removed in July 2017 due to the discovery of their paper trail.  If their paper trail had never been discovered they would have remained with their comrades...

Lisa Page and Peter Strzok were removed because Inspector General Horowitz accidentally stumbled upon their communication.  Originally Horowitz was looking at “media leaks”, and that led him to question Deputy FBI Deputy Director Andrew McCabe.  McCabe denied the leaks, but when the IG questioned Lisa Page about media contacts she said McCabe told her to give stories to the media.  McCabe and Page were contradicting each-other.

The IG asked Page if she could prove her side of the story, Page said she had texts from McCabe and gave her phone to INSD investigators…. the rest is history.  Those IG investigators, while validating the instructions from McCabe (showing he lied), uncovered the Peter Strzok and Lisa Page bias and communication that set the ground work for “spygate”.  The IG then had to inform Mueller of the compromised position...”

https://theconservativetreehouse.com/2019/03/25/a-review-of-the-barr-principal-conclusion-notification-overlaying-three-years-of-background-research/#more-161648