Bill Barr destroyed himself... He ruined himself when asked for a transcript of his phone call with Mueller, and he simply said no. It's Congress's job to investigate wrong doings. They hold the check of the Executive Branch which includes AG Barr.
If the conversation wouldn't hurt Barr or Trump... why would he NOT share that? It was on speaker phone, it's not like it was some serious national security info.
While waiting for your answer to question: "What exact crime president conducted that needs to be investigated?" , I'll return to this post for a moment.
In a clip, there was Senator Blumenthal from Connecticut... (How anybody can vote for this sleazeball and liar that said he was combat veteran in Vietnam is beyond sane)... was on CNN and MSNBC, two media houses that give voices to sleazeballs, and he threatened jail for AG Barr. The same two media houses brought in fry chicken man Cohen who also repeated these threats.
Than their ring leader, Nancy Pelosi said this: "... Yes, there is some enthusiasm” for impeachment, "but it's not about that, it's a path that is producing results and
gathering information.” -
ABCNews
Basically she's confessing that what they're doing is opposition research operation, using House of Representatives, Committee staff, tax dollars, and abusing subpoenas, to simply investigate the president for the purpose of investigating the president. That is not Congress purpose, otherwise it would be done by every Congress in every election cycle.
They're right, president is not above the law. But neither are they.