Complex sentence: Carmel and Susita were fiberglass-shelled cars that were made popular in Israel during the 1960's and 70's mainly because Government agencies were forced to buy them, thus releasing onto the market thousands of low-priced second hand vehicles.
Split into simpler sentences: Carmel and Susita were fiberglass-shelled cars that were made popular in Israel during the 1960s and 1970s mainly because government agencies were forced to buy them. This released onto the market thousands of low-priced second hand vehicles.