According to a source who spoke with Axios, White House counsel Doug McGahn had serious reservations about how much cooperation should be extended to special counsel Robert Mueller but gave in when Trump gave the go-ahead.
The Axios report calling the decision an "epic" mistake, states that within the White House several top officials believed -- and continue to believe -- that Trump made a huge mistake in the early days of Mueller's investigation into Russian meddling in the 2016 election.
McGahn has reportedly spent 30 hours being interviewed by Mueller's investigators, providing them with what was described as information that never would have been obtained otherwise.
According to Axios, Trump still believes he did nothing wrong and doesn't seem to understand the implications of his campaign staffer's actions, with one White House insider saying bowing down to Mueller is "dumb" and "idiotic."
As for White House lawyer McGahn, along with his attorney William Burck, he believed nothing good could come out of working with Mueller but gave up the fight after Trump gave his approval.
The report goes on to say that Trump's relationship with the White House counsel is strained, with Trump expressing frustration with McGahn for telling him “no” rather than "looking for creative ways to get him [Trump] what he wants."
You can read the whole report here.