I agree this is a strange claim on his part; something we've never heard before.
One possibility is Strzok and McCabe told him they were investigating everyone so he wouldn't suspect they were specifically targeting only Trump but that's pure supposition on my part.
Until he presents evidence (if he has any) it's all unfounded claims and speculation.
Noting added to that site since 2017
https://web.archive.org/web/20190627161912/https://www.deepcapture.com/