Barr was AG for Bush 41. While he may have hated Trump at one time, he doesn't anymore.
The democrats are going after Barr because they know he will soon be shaking their world up with not only indictments, but the subsequent political consequences look to have the republicans most likely end up with the Senate, House and Presidency. In addition, the present clown show that thinks they have a chance to win the presidency is trying to impress their leftist base. The democrats only chance is to give Barr the Trump treatment that's been going on for the last 3 years. If they can somehow diminish Barr they think they might diminish his ability to indict without it looking political. They truly are clowns and are living up to expectations.