OK, my theory on how Marilyn died. Keep in mind that I have been obsessed with marilyn for more than 20 years now, and I have thought about this ALOT!
It's pretty common knowledge that Marilyn kept Eunice Murray as a housekeeper. What many don't know is that Mrs. Murray was in the employ of Dr. Ralph Greenson, Marilyn's physchiatrist. Greenson was clearly obsessed with marilyn, and regularly kept her as his only patient, and frequently had her in his house to "see how a normal family lived". Mrs. Murray was planted at Marilyn's house by Greenson so he could keep tabs on his patient at all times.
Marilyn, in my opinion, had realized that the people she was surrounding herself with were only holding her back, and she was determined to get better. So one day she decided to not see Greenson anymore, and she even fired Mrs. Murray the day Marilyn died. I think that Greenson was so distraught about losing the patient that brought him success and notoriaty,
he had Mrs. Murray give Marilyn a barbituate enema in the hopes of making Marilyn believe she was about to overdose on sleeping pills, thus making her believe she still needed Greenson. What Greenson didn't know was that Marilyn's internist, Hyman Engleberg had given Marilyn a prescription for Nembutal (or am I getting it backward) and she had taken several that night. The chloryl hydrate that was in the enema had mixed with the Nembutal and killed her. I do believe her death was acciental in that respect. Mrs. Murray flipped out and called Greenson. He hurried over and together they tried to make it look like a suicide. Greenson broke Marilyn's bedroom window to try to make it look like they had to enter her room from it (as they said her door was locked), and they disposed of the enema's equipment (Murray's son simply threw the garbage in a trash can that was not located at Marilyn's home), Mrs. Murray washed the sheets to get rid of the evidence of an enema (she was found doing laundry at the time the police first arrived), and they positioned her in a way that would be consistant with an overdose suicide. They know she was postioned because there was lividity on the opposite side of her body than where she was found. It wasn't as pronounced as the lividity on her face where she was found laying becasue she had been moved before it could take hold.
So after my long winded theory, the bottom line is that I think Marilyn was accidentally killed by Greenson and Murray, becasue he couldn't fathom being with out the celebrity Marilyn brought him.
Now, as for the Kennedy's involvement, I do not believe they had anything to do with her death but they definately DID cover things up after she was gone. There is the red diary that went mising, that supposedly contained notes of Marilyn's conversations with both Jack and Bobby. Peter Lawford (JFK's Bro in law) was also a friend to Marilyn, but was loyal to the Kennedy's. I think it was he who went to Marilyn's house to recover the diary, even before he died, because he (and supposedly Bobby) were seen at her house earlier that day. When they found she died, they jumped at the chance to "clean house" to protect them from any scandal.
OK, I'm done. Sorry to be so long