The Israelis have a long standing relationship in trading military hardware with the Chinese. Another example is their air-to-air missiles the Rafael Python-3 which is manufactured in China under license as the PL-8.
I do not know exactly why the Israelis do this thing. If it is strictly for profit or if it is because they want to have a backup in case the US for whatever reason stops supporting them. Probably both. At one point their major weapons suppliers were the UK and France but after the Suez Crisis botch up the UK withdrew support. France kept selling them weapons until their other major costumers, the Arabs, said they would no longer buy weapons from them if they also sold to the Israelis. So they became reliant on the US for most weapons systems.