Why Did Jesus Leave Earth?

Questions about why Jesus left earth and how it’s possible that two Christian leaders, who both have the Holy Spirit, can have a contradicting witness about whether or not one can lose one’s salvation.

• Why did the historical Jesus supposedly leave earth? (The Jesus of the Gospels doesn’t seem to know this when questioned.)
• How is it possible that two Christian teachers, who both have the Holy Spirit, can have a contradicting witness about whether or not one can lose one’s salvation?