Who has a good explanation for this?

I assume it has to be a form of whiplash from lower falling segments forces being applied through a mechanical link.

http://websql.physics.ucla.edu/demos/mechanics/gravitational_acceleration/falling_chimney.htm

Rotational velocity. Unsupported mass falls on earth's surface at at 9.8 m/sec 2, and in this case is a rigid mass rotating around a fulcrum, so outer mass travels more distance. The average acceleration of the entire mass will be equivalent to the force of gravity, distributed in smaller acceleration from the center of gravity "inward" toward the pivot, and greater acceleration outward of the C/G. Where the balance point of your falling chimney or tree is, acceleration is nominal.

Hypewader,

Center of gravity at g. That makes sense. The next question would be why the chimney tends to break at the 1/3 point and not 1/2 point.

Or is the 1/3 point arbitrary and it is actually a function of Pi (3.141) due to the rotational aspect of the event?

I have no idea yet as to why the chimney tend to break at 1/3 of the length. However, the faster falling of chimney than the freefall is reasonable, as hypewaders said, has something to do with rotational nature of the chimney falling.

Based on T = I <FONT FACE="Symbol">a</FONT> for rotational case, equivalent to F = ma, we know that <FONT FACE="Symbol">a</FONT> increases during the falling (as T is a cosine function) while a (for free fall) remains constant. This explains why the chimney falls faster.

The lower segments of the chimney pull on the upper ones as they fall, causing them to fall faster than freefall.