There were many who didn't want him to live, because he was going to change much, for the better, but when billions $$$$$$ at stake in illegal whatevers', his enemies, ensured he didn't live to fulfil his destiny!
He was a very silly man getting involved with so many women, especially MM, as she didn't have a brain, & would've leaked/did leak possible 'pillow talk'.
His father trained his sons' in not a very nice way, to say the least.
Look at Edward trying to cover up Mary Jo Kopechne's drowning at Chappaquidick.
Robert was assassinated, because being Attorney General, he could still be very powerful & influential.
It was a real-life case of 'the sins of the father visited on the sons'. They were cursed, & had been for many years'. One of the daughter's, Rosemary, was lobotomised, that's just dreadful!
Would our world be better now if he had lived to govern for his allowable terms? I think so.