"Philip Zelikow had hired Harvard historian Ernest R. May as a consultant to the 9/11 commission. ... May felt that the commission had also compromised its promise to tell the full story of the 9/11 attacks by its refusal to tackle the issue of how American support for Israel and repressive Muslim regimes in Saudi Arabia, Egypt, and Pakistan had 'fed the anger that manifested itself on September 11.' But May was told that the commissioners believed questions about Israel and Saudi Arabia were too controversial to be addressed in the final report. 'Composing a report that all commissioners could endorse carried costs,' May wrote." p391, The Commission: WHAT WE DIDN'T KNOW ABOUT 9/11
Also see: SCANDAL: 9/11 Commissioners Bowed to Pressure to Suppress Main Motive for the 9/11 Attacks.