There's a sentence in the introduction to 日本語文法ハンドブック (a book written for teachers of beginner Japanese grammar):
寺村先生[an esteemed Japanese teacher the author of this book models himself after]は海外技術者研修協会における草創期の日本語教育に全面的に協力され、同協会の日本語教科書編纂にも大きく貢献されましたが、私[the author of this book]は海外技術者研修協会との縁により、また、若き日の寺村先生の講筵に列した者として本書の監修にあたった次第です。
My questions are:
The passive voice used for 寺村先生's work doesn't seem to make sense. Is this a case of substituting the active voice for passive as a matter of politeness?
What is 講筵's exact definition? It doesn't appear in any dictionary, although several possible meanings are inferred ("mat a teacher would sit on and lecture from")
What is the exact translation of ~た次第です here? The closest definition I can find is "reason" or "course of events", similar (I would think) to ~た理由です or ~たわけです. Is ~た次第です an acceptable substitute for these constructions?