Using periods instead of conjunctions or semi-colons [closed]

It's often described as staccato (adjective, deriving from the musical term); or parataxis (originally a Greek term).

These days it's often associated with thriller/crime writers such as Lee Child and James Ellroy, but literary authors including Hemingway made use of it. Here's a book on Hemingway, The Critical Reception of Hemingway's The Sun Also Rises by Peter L. Hays, which speaks of Hemingway's "staccato style", attributing the term to Herbert H Mosher, who identified (Hays writes): "short sentences in which the subject is immediately followed by verb, and in most, the first word is the subject; these sentences are either simple or complex, and there is frequent repetition of words. They average nine and a half words each".

According to Wikipedia, parataxis, is "a literary technique, in writing or speaking, that favors short, simple sentences, without conjunctions or with the use of coordinating, but not with subordinating conjunctions. It contrasts with syntaxis and hypotaxis."

It works well for pacy, rhythmic writing, or (as Hemingway often used it) to convey unspoken, underlying depths. It is certainly not something to look down on.