I'm not sure what you're talking about, Syria was dominating headlines for years after the civil war started. The US got directly involved, Turkey got directly involved, Russia got directly involved. Most major powers on the planet had something to say about it or some kind of involvement.

I think what you mean to say is that the world doesn't support the Syrians like they do the Ukranians, and that's because the situation in Syria is completely and absolutely fucked up compared to Ukraine.

First and foremost, the situation in Syria is an internal dispute. It's a civil war. As a base rule it is so much messier to get involved, as a foreigner, in a civil war than it is a conventional one between 2 nations. Secondly, there's no unified Syrian opposition. Hell some of them even oppose each other. There are so many completely independent groups with independent goals on the opposition side that it's basically impossible to rally behind them as a whole. Unless you're fine with supporting and supplying ISIS successor groups and other crazy extremists.

In the Ukrainian war, there's 1 clear good guy, 1 clear bad guy. In the Syrian civil war there's 1 clear bad guy, and then a giant bag of marbles with the whole spectrum of morality and ethicality inside it.

Also the Syrian civil war is 12 years ongoing at this point. You can't expect it to keep dominating headlines for 12 years straight. After a point people just become numb to it.