Answer and Explanation:
1. Because Mahayana Buddhists believe that spiritual elevation must be achieved through acts of compassion for other individuals. They believe that they must seek the spiritual enlightenment of all living beings and thus they will find their own enlightenment, promoting the good of society. Theravada Buddhists do not follow these precepts and are therefore seen as selfish by Mahayana Buddhists, who believe that selfishness is a way to slow their spiritual growth.
2. Theravada Buddhists believe that Buddha affirmed that each person should seek his own spiritual enlightenment individually, being his own example and not following other people, but creating his own methods of success and ignoring the elements around him. Mahayana Buddhists do not follow these precepts and are seen by Theravada Buddhists as exaggerated who spend more time worrying about the collectivity than strengthening themselves, ignoring Buddha's precepts.
3. Both points of view are correct in your statements, in my opinion, because the search for spiritual enlightenment should be done in the way that the individual believed that it is correct and that it will promote good and comfort. In this case, both the search for collective lighting and the search for individual lighting are correct, as both promote beneficial results.