なぜならそこにあるからさ。

because; the reason is; if you want to know why

there (place relatively near listener); there (place just mentioned); that place; then (of some incident just spoken of); that (of point just raised); you

at (place, time); in; on; during; to (direction, state); toward; into; for (purpose); because of (reason); for; with; by; from; as (i.e. in the role of); per; in; for; a (e.g. "once a month"); and; in addition to; if; although

to be (usu. of inanimate objects); to exist; to live; to have; to be located; to be equipped with; to happen; to come about

from (e.g. time, place, numerical quantity); since; from (originator); by; because; since; out of (constituent, part); through (e.g. window, vestibule); after; since

-ness (nominalizing suffix indicating degree or condition); (sentence end, mainly masc.) indicates assertion; come; come now