Given that Hariri's death triggered a popular uprising known as the 'Cedar Revolution', which overthrew the pro-Syrian government in Beirut and led to Syrian troops being forced out of Lebanon after decades of peacekeeping since the Lebanese civil war, it's difficult to see what possible motivation the Syrian government may have had for assassinating Hariri - though one can certainly see how certain other countries in the region may have benefited.
Having grilled Assad on his alleged involvement in that macabre deed, Amanpour went on to tell her interviewee, to his face, that the US government was 'actively seeking' to depose him by force:
"Mr President, the rhetoric of regime change is headed towards you from the United States. They are actively looking for a new Syrian leader. They are granting visas and visits to Syrian opposition politicians. They are talking about isolating you diplomatically and perhaps a coup d'état or your regime crumbling."
Comment: South Korea's Foreign Minister told CNN's Christiane Amanpour something that likely made her throw up a bit in her mouth... that Donald Trump deserves a lot of credit for making this historic meeting happen...
Trump in turn gave a shout out to Xi Jinping, who was no doubt also instrumental:
In summary, the two Koreas have agreed to: