whatcha think? It’s red pill time dude!
The different effects are simply the result of the direction of the blast wave.
At Hiroshima, the bomb was detonated at about 1500ft altitude. Directly underneath it the blast wave was going straight down, so that it stripped the leaves and small branches off the trees, but left the big branches in tact.
The further away from the centre of the blast, the greater the angle of the blast wave, and the more likely that buildings and trees would be blown over sideways.
Some of the observed effects are a result of Japanese architecture, and a tendency to build light walls.
I suspect the bending on the stairwell is a result of compression from above (or more correctly slightly to the side.
Mt St Helens had a primary blast wave directed upwards, and about a 40 degree angle – so it flattened all the trees in its path. A lot of the damage done was as a result of flood waters from the melting ice off the mountain mixed with lots of ash and debris (the ash would raise the specific gravity of the water, and make it easier to pick up and float objects that would sink in ordinary water.
Tunguska was another air blast site, but very much higher, with a very much wider radius of destruction. Again, trees directly under the blast centre were left standing.
Most bombing of cities was done with bombs with delayed action fuses, designed to bury underground, then explode upwards, creating as much damage as possible with the flying debris.
As to bowed trees, when you lay a tree across a valley, then heat it to boiling point with a pyroclastic flow, then cool it again, it assumes the form that gravity deformed it too while it was soft.
Woodworker regularly use steam boxes to bend wood to complex shapes – the volcanoe just provided a large natural steam box.