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.

If the person who wrote it didn't proofread it, then the content likely hasn't been thought through.

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.