It's the kind of typo a spellcheker would overlook. Maybe the article could have used more proofreading but so what? Somtimes content is more important than presentation.
every writer knows its notoriously hard to proofread your own writing. you know how it is supposed to read and your brain just kind of goes on autopilot.
As soon as I see a dumb typo like that the rest of the article imo is now trash