In Israel, when a law is broken, the police investigates, the prosecutors charge, and the courts try. Nobody even charges that any law was broken. In any case, the Knesset never investigated anything, and has no tools for such an endeavor, not even subpoena powers. If you are a historian, you should refer to facts, not what you THINK must have been the case. All the investigations you mentioned were conducted SOLELY by the police. The leftist NGOs do not want to hide anything, they haven't broken the law as far as anybody could tell, or the one who could tell would have notified the police and there would have been an investigation. But nobody likes to be picked upon. Blacks don't like to be stopped in the street and questioned what they were doing in a white neighborhood solely because they are black. (It is now against US law to do such questioning based on color alone.) What the Knesset should do is pass some laws against foreign contributions to political organizations, or laws against contribution by well-defined enemies. Nobody will object to such laws.
Four Libyan soldiers said killed in battle with Islamists in Benghazi (Reuters)
from the article: Rightist MK expected to head probe into Israel's Leftist NGOs