'From that' would mean from the clue he has just found (in the previous picture). Jerry has explained the rest. 👍

Batman started in Detective magazine i.e. he follows clues to the bad guy. So, the graphic cell means: he was following clues that led him (blossomed) to more clues, which ultimately brought him to where he was now.

Not enough context! Leads could refer to clues or hints. A detective follows up leads when working a case. Batman is said to be a detective so that is probably it.

“Leads” are like clues so this is a noun in plural form not the verb “lead”. In plain meaning, it says that clues became more obvious to him and so those clues brought him to some point