The letter is a post on his own blog . Hard to distill into a summary so I recommend reading it get more context. But it seems to have boiled down to:

• How It Was:

  • Strong adherence to the "don't be evil" ethos, focusing on societal good over profits.
  • Open, transparent communication and decision-making processes.
  • High morale, with a culture of learning from successes and failures.
  • Work focused on benefitting the web and users, rather than Google's immediate interests.
  • Collaboration and lack of internal silos, encouraging innovation and autonomy.

• How It Is Now:

  • Shift from user-centric to Google-centric, and then to individual-centric decision making.
  • Eroded transparency and increase in organizational silos.
  • Decline in morale and a culture of distrust between employees and management.
  • Focus on short-term financial gains leading to layoffs and defensive employee behavior.
  • Lack of clear vision and leadership, resulting in confused and ineffective management.
  • Overall deterioration of Google's unique, innovative culture and values.