Addressed to the target? Unless they have a jihadi inside the Synagogue.
No, someone was to intercept the delivery before the package reached the address on the label. Like the pot delivery to a mayor of some Southern town- it was supposed to be diverted before it got to the innocent target.
A synagogue delivery will be less suspicious than some apartment.
Or, there are radical Rabbis expecting explosive shipments!
Has anyone said what the explosives were, how big, what type?