One major reason the league of nations failed
was that it
(1) was not included in the versailles treaty
(2) was controlled by communist russia
(3) frightened many nations with its large
military force
(4) lacked the support of many of the major
world powers during crises

1) Definitely no because it was actually included in the Versailles Treaty and it couldn't be the reason of the LN failure.
2) Ehh, no. Soviet Union  was expelled from LN in 1939 (while LN ceased to exist in 1946)
3) Nope..
4) I think this is the right answer. The major reason of failure of LN is that it couldn't prevent the WW2 (and the primary purpose of this organisation was to prevent military conflicts. And as we can see, LN had layed an egg)

Yes, some people used the depression to the max. not everybody had stocks, and those that didn't bought many things inexpensive, so that when prices rose again, they were much more richer than beforehope this