Translation:The leader of this organisation was in the past the Minister of Education.
Not clear if "dahulu" is meant fo the "pemimpin organisasi ini", i.e. "past leader of this organization" or for the "Menteri Pendidikan", i.e. "former Minister of education". If it is the former, the sentence in English could read: "The past leader of this organization was the Minister of Education", if the latter: "The leader of this organization was formerly the Minister of Education".
I think for noun phrases, ini/itu always come last, so dahulu is referring to the current leader's former career.
Minister for X is used in some jurisdictions/contexts.
All the ministers listed here use 'for'
Unless Indonesia has multiple education ministers, she was THE minister of education.