that was the narrative at the time,that the DNC had been hacked,but it never held up under scrutiny.it was most likely an inside job,someone from the DNC leaked those e-mails.
https://thehill.com/policy/national-security/312767-fbi-never-examined-hacked-dnc-servers-report
https://www.thenation.com/article/a-new-report-raises-big-questions-about-last-years-dnc-hack/
but probably the strongest case is made by former NSA analyst William binney,part of veteran intelligence professionals for sanity (VIPS),along with fellow member and former CIA ray McGovern.another strong ciriticism comes from former colin powell chief of staff col larry Wilkerson.
I won't link blast ya,and I am not even trying to change your mind.just pointing to the people that have a very strong counter-narrative,and are worth the listen.
was the DNC hacked by Russians or some other state actor? possible,but it doesn't stand up well to scrutiny.
whereas the "leaked" narrative does hold up far better,and is confirmed by the entities that published the emails.both DCleaks and WikiLeaks.