“Explanations exist; they have existed for all time; there is always a well-known solution to every human problem — neat, plausible, and wrong.”
All parties accept that the situation in Syria is deeply complicated. On one side (which I guess would be the group against the pre-war status quo) there continue to be non-violent protestors against Assad. They are mixed in rebel-held areas with Sunni militias supported by Qatar and perhaps Saudi Arabia, and radical forces of mostly foreign extraction like al-Nusra that want a Sunni state at the expense of moderates and other religious groups.
This contrasts with an Assad regime supported by (and protecting) the relatively small Allawite Shite minority. They are given strong support from Hezbollah and thus considerable support from Iran. They also get large amounts of sophisticated weapons from Russia.
This is not even going into the Kurds and their involvement in Syria and Iraqi Kurdistan, Turkey as a NATO nation dealing with a refugee issues, whether escalation could lead to strikes inside the borders of Israel. Many other countries in the region have been supporting one side or the other, or tried to be neutral (Lebanon) but failed or had to deal with the massive refugee crisis which will not end anytime soon.
So when U.S military intervention shows up, remember that any solution to a complex crisis that is neat, elegant, plausible also has another attribute- it’s totally wrong.