75% of all syntax errors disguise weak arguments. That is to say, the “technical” mistake often serves a purpose, albeit unintentional. The writer does not *intend* their iffy grammar to act as scaffolding, but the iffy grammar certainly helps. It can obscure a shoddy construction and many logical leaps.
I’ve witnessed this in my own writing. It just happens. When we’re not sure how to complete a thought — or are afraid to — it’s easier to type _something_ and move on, imagining that we’ll fix it later.
But we don’t always get back to it later, and the more times our eyes pass over what’s actually a mistake, the more it looks o.k. to us. (Our ears are less easily lulled into complacency, but that’s another conversation.)
Untangling tangled syntax, then, is like fixing a wobbly table. First you remove the wad of folded-up napkin that’s been stuffed under one of the legs as a temporary solution. Then you lean on the table to gauge the extent of the wobble.
Then you decide: Brandish a saw and shorten one of the legs? two legs? tighten some screws? or just toss the whole mess in the dumpster and move on to the next table? A good editor will help you make these decisions.