It is just grammarly wrong.
The author was wrong or typo.
知識欲が行き過ぎたが故の職業病なのぉ？ is correct.
知識欲が行き過ぎる故の職業病なのぉ？ is also correct.
According to Japanese teacher's blog, You can use infinitive verb, that is 行き過ぎる故の in this case.
However, you cannot use 行き過ぎた.
naruto-san said a different thing, but I trust what I have ever seen and learnt and what the Japanese teacher said...
(I am sorry for saying here. I cannot add a comment to naruto-san due to my lack of reputation because I am a new contributor.)
As you said, ～が故に/の or Noun + 故に/の (e.g. その美しさ故に/の) is common.
However, it is almost used as literal language and We rarely use it in daily conversation.
Indeed, we occasionally use it in verbal communication.
Occasionally, you want to use a literal language or difficult word, don't you?
That is about it.
That is the situation in the Manga though it is grammarly wrong...