I agree with this summary. It's not a trend, but a rediscovery of the tradition and philosophy of "do one thing and do it well". Small/minimal libraries do not necessarily mean "proof of concept" or "tiny subset of features". They usually aim to provide one generic, reliable and reusable feature per library/module. There is great value and flexibility in that approach.
As another person noted, it's also a reaction against frameworks like jQuery, Bootstrap, Angular, Polymer, and yes, even React. Some people prefer to combine only the functions they need, rather than include an all-in-one dependency.