Which statement is the "cause" when the following sentences are combined with regard to the position of "for"?
1. Superstitions about names persist today.
2. Parents often name children after leaders.
3. Parents often name children after entertainers.
4. Parents avoid the names of heinous criminals.
Here is my combination:
Superstitions about names persist today, for parents often name children after the leaders and entertainers, and avoid the names of heinous criminals.
Your choice of using "for" to combine the sentences in a logical way is correct. The use of the word "for" is similar to using the word "because."
[Y]ou can use the word “for” as a conjunction to mean “because” or “since.”
You organization of ideas seems to follow this first pattern: three sentences are similar in that they each have the word "parent" in them. The only one that does not then becomes the statement that creates a context for the rest of the "parent" sentences. The next method of logical organization on your part is found in placing together the "parent sentences" that are similar, and isolating the one divergent, diametrically opposed "parent" sentence. In other words, there is a positive reason in the naming of children after two kinds of people: leaders and entertainers. At the opposite end of the spectrum are names that are avoided because they are the names of "heinous criminals."
The basic premise of the thought presented is that superstitions about names exist. You go on then to support this general statement with specific examples—separating them into positive aspects by which parents choose baby names, and negative aspects that prevent parents from choosing certain names…and you place "for" in the perfect spot.
It is very interesting to study this kind of "word problem" in that you look for the general statement and support it with the specifics— while the specific examples differ greatly in nature and need to be further "categorized" in relation to each other, but separated from the general statement they support.