In the following sentence,
as far as I understand, the whole part before ばかり is, grammatically, a noun, say:
But then, I don't understand this usage of ばかり. Maybe ばかりであるから means something like だけあって or だから当然 ? But then, isn't a subject lacking?
The subject could be the topic from the previous sentence, but from context I don't see how it would make sense. This is a link to the page this text was taken from.