[Did Peter Strzoh know that emails from Hillarys server went to the Chinese?]
The interim system may have been detected simply through routine pattern analysis of the internet data.
Too many “mays’ and “maybes”.
The KISS answer is that Chinese security have the best hackers, and were able to find these “breadcrumbs” through Hillary and ALL other “private” servers running around DC.
It sure is strange that multiple high level government officials, ALL with TS or SCI designations, and all within the Obama administration, were set up so close together and emailed each other so often.
There is a reason that American security used to be strong, and is now not strong - elite privileges allows to the Pigs More Equal.