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it would be incorrect to use it here, and it wouldnt rhyme either
potomu, chto == because
and "za to, chto" is more like.. "as a consequence of"
may be i could explain by example.

lets see..
...

in this context, "za to, chto" means "because".
so the translation is:
i love you because you exist
because you are here and simply nearby
i love you because you are the way you are
because you...