1. They have common interests and values. They are all engaged in the education industry, are well-known teachers of New Oriental Online, and have the same or similar professional background and experience. This gives them a deep common topic and a basis for mutual understanding.

2. Long-term mutual support and encouragement. As they work in the same industry, there will definitely be opportunities for mutual exchange and support. Their friendship may be established and deepened in the long-term exchanges.

3. Similar experiences and life trajectories. Xu Tao and Tang Chi may both come from educational families, or they both studied in famous universities at home and abroad. These similar backgrounds may make them have the same enthusiasm and understanding of education. At the same time, they have made remarkable achievements in their careers, and this similar life track may also strengthen their friendship.

4. Mutual trust and understanding. Xu Tao and Tang Chi may encounter similar challenges and difficulties in their work, and mutual trust and understanding can provide them with a supporting force for mutual dependence and common progress.

In a word, the good relationship between Xu Tao and Tang Chi may be due to their common professional background, long-term mutual support and encouragement, similar experiences and life trajectories, and mutual trust and understanding. This friendship not only helps them succeed in their careers, but also enriches their personal lives.