Put together a number of variations on sth.

Hello everyone,

I would be so thankful if you could express the phrase "put together a number of variations" in a different format. Why should someone put together a number of variations? Can variations actually be put together? For which reason? I also should confess that I'm not totally sure about what does the author mean by referring to "the same two-step variation".

Things are even worse than I’ve portrayed them, at least in the United States. Not only is increasing income not associated with increased well-being over the past several decades— but well-being has actually decreased over this time period. Sensitivity to relative income definitely accounts for part of this reduction in happiness, but it’s not the whole picture. Something else is going on that can’t be explained by these kinds of factors. In the book Bowling Alone, Robert Putman first put his finger on what was missing in all of these analyses: social. Putnam and those who have followed him have put together a number of variations on the same two-step theme. First, social factors substantially contribute to subjective well-being and life satisfaction. Second, in modern nations like the United States, these social factors are in decline. Let’s take these in order.

Reference: Social: Why Our Brains Are Wired To Connect.