Israel and Hamas may currently be locked in deadly combat, but, according to several current and former U.S. intelligence officials, beginning in the late 1970s, Tel Aviv gave direct and indirect financial aid to Hamas over a period of years.
Israel "aided Hamas directly -- the Israelis wanted to use it as a counterbalance to the PLO (Palestinian Liberation Organization)," said Tony Cordesman, Middle East analyst for the Center for Strategic Studies.
Israel's support for Hamas "was a direct attempt to divide and dilute support for a strong, secular PLO by using a competing religious alternative," said a former senior CIA official.
https://www.upi.com/Business_News/Security-Industry/2002/06/18/Analysis-Hamas-history-tied-to-Israel/UPI-82721024445587/