Just because chance had been ruled out as an explanation did not prove telepathy must exist; there were many other ways of getting positive results. 

1 as为介词，意为“作为”，在because从句中作方式状语。

2 must在此表示推测意义，意为“肯定、必定”

3 原文中just because从句作了主语。这是不规范的英语，是口语中说话人思考不周而犯的口误。应该改为:

The fact that chance had been ruled out as an explanation did not prove telepathy must exist; there were many other ways of getting positive results.