A lot of folk miss the tactical significance of Suribachi being taken out of the Japanese inventory.
The Mt. gave the Japanese overwatch on the entire island, including the beaches. It was also a fortified platform with much artillery in armored bunkers and caves from which the guns could fire.
When the mt. fell, a significant portion of the indirect fire, heavy arty, was lifted from the beaches which allowed greater log flow to the Marines ashore.
It also deprived the Japanese from an observation post from which all USMC movements ashore could be watched and reported.
PS.
For those interested, Lions of Iwo Jima is a good read.
http://www.amazon.com/Lions-Jima-John-MacRae-Books/dp/0805090177