Explanation:

The spiritual aspirant having complete knowledge from all sides by achieving it through sharp analysis will straightly catch Satguru and serve Him with full determination and there is no need of any spiritual knowledge even from Satguru. The spiritual knowledge helps only to detect the Satguru. If Satguru is detected by your sharp analysis of spiritual knowledge, there is no need of spiritual knowledge from Satguru also. Gopikas were divine sages, who have already detected the human form of God as Krishna. They straightly loved and served Him with full determination and Krishna did not preach them any spiritual knowledge as there was no need of it. They were only tested by the Lord in the strength of their determination that has to be maintained forever. Those sages who maintained the same strong determination could withstand the tests and succeeded to get the eternal grace of the Lord. Some of them could not maintain the same strength of determination during the tests and hence failed.