I will drop my 3 cents here
I think Charlie was killed because he was gaining popularity which would set him as future president candidate, but due to his traits he was unacceptable to powers and couldn't be allowed nowhere close to the office. I don't say it would happen by the next election but it eventually would.
Trump is really dead for his voters base, he shown himself as just another one of them and if he gonna get any votes in the future it will be based purely on choice of lesser evil but never on trust or hope.
In such a situation Charlie could come out as an absolute winner, but there is an issue, mossad have nothing to keep him by his bollocks, he was clean and right, he would be truly independent, it could not happen and had to be stopped
I also believe trump was involved in assassination, not by making the decision but by turning blind eye on the plan and going along, which were the reasons i don't know, but taking into account thet trump is generally stupid, anyone could convince him with a bit of fake stories whispered into his ear and ego patting.
I also believe awkward situation in the memorial was the moment Erika understood the trump was involved and this is the reason for hail of satan, an subconscious response to shock caused but sudden understanding.