Why is there "was" instead of "were" in this conditional type 2? [closed]

Why is "was" used here while there must be "were"?

If the foe-caster made the correct observation and the campaign was successful,.......

conditional type-2

Start by forgetting what you have learned about "zero, 1st, 2nd, 3rd conditionals". Those are not terms for distinct things in English; they are only teaching devices for introducing learners to conditional constructions. You have now progressed beyond the point when they are useful.

Without more context it is impossible to say exactly why the ordinary past form of BE is used here, but I would guess that it represents an ordinary ‘backshift’ into the past tense in order to express a condition and consequence which obtained from time to time in the past.

PRESENT: If/whenever the forecaster makes the correct observation and the campaign is successful we {are able to/can} do such-and-such.
   ↓ backshift
PAST: If/whenever the forecaster made the correct observation and the campaign was successful we {were able to/could} do such-and-such.

This is quite a different thing from the "2nd conditional", which is ordinarily taught as a conditional construction in which the present tenses are ‘sideshifted’^† into past forms without person/number inflection (what traditional grammar calls the ‘subjunctive’) to express an ‘irrealis’ (unreal or counterfactual) condition:

REALIS: If the forecaster makes the correct observation and the campaign is successful we {are able to/will be able to/can} do such-and-such.
   ↓ sideshift
IRREALIS: If the forecaster made the correct observation and the campaign were successful then we {would be able to/could} do such-and-such.

Note that with the sideshift this refers to non-past (present or future) conditions and consequences.

Note, too, that your clause may represent an irrealis use: the ordinary fully-inflected past forms are often used instead of the ‘subjunctive’ forms in speech and colloquial writing. I suspect that this will eventually prevail in most contexts, but I advise you to stick to the ‘subjunctive’ forms in irrealis contexts: this is obligatory in formal registers, and entirely acceptable in informal registers.

^†_{Sideshift is a term of my own invention, not something you can employ elsewhere and be understood.}