Well, I'm not sure if I can help properly.Context is important. I'll just give you a literal explanation. I hope it fits with the content of the song. 増える (fueru) means to increase or to multiply. If you see 増えた(fueta) it's just because it's past tense of the verb. から in this case means "because". other meaning kara has it is "from" (e.g. time, place, numerical quantity) and since|from (originator). a rough translation would be= becuase it increased/multiplied. (actually something or someone increased by someway).

Looks like you've received a very thoughtful answer already FYI Rikai-kun online is a very useful resource for kanji. Cheers.