Sometimes two nouns joined by the word "and" refer to two distinct things, and sometimes they both describe one thing that is a combination or fusion of two different things. For example, in the sentence "the doctor and researcher lives in New York", the subject is one person; that person is "the doctor and researcher", and as a singular subject it requires a third-person singular verb. In the sentence "the doctor and researcher live in New York", the subject is two people; one person is the doctor, and the other person is the researcher. As as a plural subject, it requires a plural verb. In your sentence the phrase "encouragement and acknowledgment" is ambiguous with regard to number. It can mean "encouragement" and "acknowledgment" as two different activities, or it could mean "encouragement and acknowledgment" as one single activity that combines both "encouragement" and "acknowledgment". The fact that the writer used the third-person singular verb "was" for the subject "the encouragement and acknowledgment" means that the phrase "the encouragement and acknowledgment" is a singular noun describing one thing that is both "encouragement" and "acknowledgment" at the same time.

Whether a compound subject takes a singular or plural verb can be tricky. In this case, 'encouragement and acknowledgement' requires the singular verb because it is essentially considered just the one idea - support. There is a strong enough link between 'encouragement', 'acknowledgement' that when you link them with an 'and' as a compound subject, they assume or take on one idea which requires the singular verb.