I think it’s similar to another construction that we already know: “voy a hacer algo”, when we say we’re going to do something. You know how we say, “Voy a estudiar” (I’m going to study), “Va a comer allá” (he’s going to eat there) and so on. This construction is IR+a+INFINITIVE.
We can use a similar construction with ayudar (although with a different meaning): AYUDAR+a+INFINITIVE. The “a” is just a part of the overall construction of the phrase.
There are a number of verbs that use prepositions such as “a”, “de”, or “con” in this manner. The topic is “verbs which require prepositions”.
