Because the moslems are like any other kleptocrat, they think if the steal the USA they will have the power of the USA.
It is like the old cartoon of Hagaar the Viking who can't figure out why the spigot/faucet he stole does not have water magically flowing out of it.
The Imans of mainstrean islam think that by "taking" the USA they will have the industrial power of the USA.
That's like that old joke about the Mexicans. "The Americans stole half my country." "Which half?" "The half with all the good roads!"