Grammatically all of them seem to be correct and meaningful but some have different meaning and interpretation. (I'm not sure which meaning is your exact aim, I just guess it is the one which could be found in the first sentence.)
For example, as I read the 1st sentence, the foolishness of the subject is more emphasized while in the 2nd sentence being defeated by the enemy is bold.
Probably we can interpret them in this way:
1-You are idiots, "that's why" your enemies defeated you. (The cause is focused.)
2-Your enemies will "defeat" you, you are nothing for them. (The cause is not focused.)
I'm eager to know native English readers' opinion as well.
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