I was a bit surprised to discover that the Merriam-Webster online dictionary defines paragraph as:
a subdivision of a written composition that consists of one or more sentences, deals with one point or gives the words of one speaker, and begins on a new usually indented lineI don't know just when that particular definition crept into the dictionary, since for me, who "learned" to write (that's obviously debatable) many years ago, a paragraph of one sentence was always oxymoronic. A paragraph was supposed to be a collection of sentences that dealt with a particular topic, preferably (if you'd studied Freshman English) with a topic sentence, some mid-paragraph development, and a closing sentence at, rather obviously, the end. I long ago abandoned any feeling of commitment to such a structure, but even so I still find myself clinging to the "concept" of a paragraph as a division of a written work that stands alone within that work because it has an internal consistency and its content is distinguishable from the content of other paragraphs. Thus, when I read newspapers and magazines, both print and online, including from mainstream publications whose writers no doubt are journalism school graduates, I continually find it strange that I'm reading one-sentence paragraphs. It's hard to find much development of an idea when the topic sentence is the only sentence.