It's been widely reported. Much of the cabinet hates Musk.
Look at it from their perspectives. They've sold their souls to grasp at power, and now that they have control over massive federal agencies, this motherfucker starts trying to fire their staff and cut their funding.
There are tons of easily found articles. I saw a bunch regarding the recent email. Here's merely one, and it references the differences and how the cabinet is not all on the same page. I remember seeing some references explicitly to specific cabinet secretaries or top appointed agency officials directing their agency to disregard it. It's interesting.
A Trump administration official said the move led to “some annoyance” among not only top officials, but even some Cabinet secretaries, adding that the secretaries “are in charge of their own agencies and need to conduct their own reviews for where cuts may be needed.”
“The president respects the decisions of his Cabinet secretaries to tell their staff not to respond to that email because they did so out of interest of national security and they don’t want to obviously risk confidential information.”
Meanwhile, those working in the executive office of the president, for example, were told they do not have to respond and are considered exempt from the email.