IMO because he knew he dumped EC on FEDERAL land and also because he wasn't sure the Marine Corps wouldn't involve themselves. (I guess he didn't realize they'd be embarrassed and distance themselves from this heinous case???)
I dont believe that the Marine Corps distanced themselves from the case at all. There are 4 jurisdictions involved.
1. San Bernardino County - They started the case from the beginning, not the Marine Corps. The case started when there was a missing person from Joshua Tree State Park (even though we now know thats not the case). Joshua Tree State Park is in San Bernardino County. That's the correct jurisdiction.
2. Bureau of Land Management - A Federal Agency. Yes, they could bring federal charges, but crimes like this are often handled at the County Level. Back to #1.
3. Riverside County - Her remains were on the other side of the county line in Riverside County. Riverside County wont trump the jurisdiction of San Bernardino because San Bernardino has an open, active case. Back to #1.
4. The Marine Corps - Yes, the crime happened while he was still in the Marine Corps. More than likely, the Marine Corps is not going to bring him back to active duty status and jail him in the brig just so they can carry the case. SJA (Special Judge Advocate) has absolutely prosecuted murder cases with convictions, no problem. But if they bring him back, they have to pay him, feed him, clothe him and provide him medical and dental, as well as for his family. His dishonorable discharge would happen as part of his sentencing at that point (BCD - Bad Conduct Discharge). When cases like this happen, and the civilian authorities are the lead agency on it, the civilian authorities keep the case unless they refuse to prosecute. In that case, the SJA would most likely pick up the ball and run with it. Back to #1.
BTW, I heard it mentioned here a days ago..... Yes, CL has an honorable discharge from the Marine Corps. After his conviction, that can easily be rectified to a BCD via administrative paperwork. They would not have to bring him back to active status to accomplish this. *edited to add* That would effectively wipe out any benefits that he would be entitled to (i.e. G.I. Bill, VA Home Loan, VA Disability Benefits, Etc...). G.I Bills can be used by spouses or children. The Vet has to sign them over. If he gets a BCD, NL or their child will not be able to access them. The benefits just simply disappear.
Hope this helps.