We all know Mary that you glider pilots are eagle-eyed sky gods (you've told us on here often enough

) but the fact is us SEP pilots are mere humans and prone to make human errors. Clearly, the pilot of the infringing aircraft made such an error - the report mentions distraction. A common human failing.
Thankfully on this occasion the landing pilot had sufficient presence of mind to make effective avoiding action, and he should be commended for it