Terrorists from over 80 countries fighting in Syria but WHY NOT AGAINST ISRAEL?

Tens of thousands of foreign militants from over 80 countries, including Saudi Arabia, the US and European countries, are fighting in Syria, a source close to Syrian presidency says.
The source who spoke on condition of anonymity stated that more than 4,800 Saudi nationals, 3,000 Palestinians, 2,700 Tunisians, 2,000 Algerians, 800 Kuwaitis, 1,300 Americans and Europeans, 400 Afghans, 4,500 Iraqis, and 350 Chechens are among the foreign terrorists waging war against Syrian government in the Arab country.
The source added that the identity of 90 percent of the Islamic State of Iraq and Levant (ISIS) members were not clear.
Al-Qaeda linked al-Nusra Front and the Islamic State of Iraq and Levant are spread in 30 percent of Syrian territories.
Infiltration of foreign militants to Syria, by the help of their Western and regional supporters has been a grave concern for regional countries.
The bloodshed has already caused security problems in Lebanon and in Iraq, while Turkey, one of the main supports of the war, is also facing unrest which is seen to be partly due to its controversial policies to back the violence against Syrian President Bashar al-Assad.