So what are the attributes of characteristics of the twin tower collapses which to the layman seem counter intuitive?

How does mass which was "locked up" in a standing structure... become the force (mass) which destroys it?

Basic understanding of how structures work is necessary. In the broadest sense the forces (mass) are "aggregated" and "directed to more and more robust elements and eventually to bedrock/foundations.

So... a desk has 4 legs which transfer the weight of the desk and contents to the floor slab it is on... That floor slabs has many "objects/weights" bearing on it - super imposed loads. The slab is designed to support itself and the anticipated super imposed "live" and "dead" loads... like wall and mechanical equipment. Each slab is supported by beams and girders. The slabs inside the core were supported by beams and the beams by girders. The slabs outside the core... (column free open office space) was supported by the perimeter columns and a belt girder surrounding the core. The belt girder was supported by the 24 perimeter columns of the core.

The system repeated for each floor. The columns at each level at to support all the loads from all the levels above it... and so were progressively strong from top to bottom.

What happened to the twin towers is that a single floor slab was over loaded when material from above fell onto it. The slabs itself could break up or the joint between the slab and the perimeter columns and or the belt girder would fail. If these connections fail... the slab breaks free and drops.

Each element... slabs, beams, bar trusses, bearing angles, bolts, welds etc. were designed to support the live and dead loads. The twin tower slabs were designed to support 29,000,000 pounds divided into the number of connections that the slab had to the belt girder and the perimeter column panels. Note that the double bar trusses were supported on spandrels at the perimeter because they were spaced at 80" on center... and the columns were at 40" centers... spandrels "moved" floor slab loads to the other columns... to "share" the loads.

Core side (double trusses shown in purple, Belt girder in red, transfer girder in yellow)

What failed when the floors were over loaded were the connections. The slabs broke free, dropped to the slab below and the process rapidlyy repeated until all slabs were destroyed/separated from the axial support structure. It's likely that after a number of slabs broke free and were falling the force of the impact on the lower slab was sufficient to shatter it. By the time this growing mass of broken slabs and contents tore through 10 or 15 slabs (we don't / can't know the number) the impact was shattering the slabs and contents to dust and gravel sized rubble.

The tower was 95% air by volume... and so if the perimeter at the base of the tower had maintained its integrity.... the entire tower inside the perimeter would be a compact mass of about 4-5 stories high. But a significant amount of the concrete was turned to dust and carried aloft on winds.

The perimeter at the lower reaches of the towers did not maintain their integrity and debris spread away from the tower... like a pile of gravel or sand would.

The above concepts are fairly simple to understand even for the layman. But to do so they need to know what the structural system was... and the most basic even intuitive understanding of structure. A table is not supported on dowel sticks because dowel sticks cannot support the weight (load) of the table top and the dishes etc.

Designers will use the least amount of material to do the job because it costs less to use less. However designs have a margin of error built into their designs. A table may support 50 pounds or 100 pounds but collapse when 200 pounds is placed on it. People understand this. It is not rocket science.

Laypersons would likely have difficulty understanding Euler self buckling (from their own weight)... of columns which are too slender.

Early on the term pancake collapse was used and this was taken too literally. But it was a runaway progressive collapse because the building's slabs were not designed to arrest such a collapse... slabs were designed for "normal office floor loads".

With a little understanding of the structure and intuition the mystery of the collapse becomes trivial.

No need to demonstrate what essentially everyone understands.

Having said that these building collapses and the the designs of these towers have been instructive to designers of high rise towers.