Religious Human Weakness In Groups

There is a common belief that:

1. Jews sin only as individuals, not a group.
2. The Torah greats are in charge of preventing group sin.
3. The Rabbis are successful at this mission.
4. Torah observance is not “improving”; we have always been perfect.

How, then, do we explain this fact, from Wikipedia?

המעבדה הראשונה לבדיקת שעטנז הוקמה בארצות הברית בשנת 1941 על ידי הרב יוסף רוזנברגר זצ”ל.

Or the far-later founding date of the first certifiably kosher Klaf (ritual parchment) factories?

Etc.