Why did the former president fire the head of the Department of Homeland Security Cybersecurity after losing the 2020 President Election?

U.S Intelligence has confirmed that Russia interfered during the 2020 President Election on the behalf of the former president to push misleading or unsubstantiated allegations against President Joe Biden to U.S Media Organizations trying to undermine public confidence in the election process and exacerbate sociopolitical division in the U.S. U.S Intelligence has confirmed that Vladimir Putin was not only aware of but directly involved in the operation to hurt Biden and give the former president a boost.

https://www.odni.gov/files/ODNI/documents/assessme...

Why did the former president bar U.S Press from the White House while meeting Vladimir Putin's cabinet in 2017?

Directly after his inauguration DT made major fan fair of inviting Vladimir Putin's cabinet to the White House however he barred the U.S Press from the meeting and reports have said the former president gave them full unrestricted access to the White House while there.

On February 20, 2021 an ex-KGB agent said the former president had been a Russian Asset Since 1987.

https://nymag.com/intelligencer/article/ex-kgb-age...

To me this is very damning, I believe the Mueller investigation was a sham because as we've seen/has been shown physically/in writing the former administration flat out lied, even under oath for DT and the AG misrepresented the report from the get-go. If anything the investigation should be reviewed now.