If Israel is really doing this, then there has to be some multidimensional strategic interest which is not apparent on the surface. Also, Israel would not have done this without at least consulting with the U.S. as to what the ramifications may be.
Except for Carter, Obama, and Secretary James Baker, who were all notably and vocally anti-Israel, Israel has always worked hand in hand with America and American interests. Especially with the Trump administration, it is very doubtful that Israel would do this deal sub-rosa and then just 'notify' the U.S. after the fact. This would not be characteristic of how Israel usually conducts foreign policy vis-a'-vis America.
Also, China has sold arms to Syria including advanced shore to ship missiles as well as other advanced systems. China has some support ties to Hamas, Hezbollah, and the PLO. These ties may be only perfunctory but still they are enough to give pause. And China's attempted takeover of parts of Africa has brought them into conflict and competition with some Israeli interests there.
This 'deal', if it is real, is likely much larger and more globally elaborate than what is being reported. And, it is very unlikely that Israel would act against the interests of the Trump administration and America. We are only able to see the tip of the iceberg. No doubt there is much below the surface that we simply do not know.