String to Column KQL

I want to extend DetectionMethods which is string data type in emailevents table. But this may apply to other tables and situations,

EmailEvents
| take 1000
| extend kqlt=parse_json(DetectionMethods) 
| extend DM_Phish=kqlt.Phish, DM_Spam=kqlt.Spam

Above results in adding this, 

Values are still displayed as ["Value"] and not Value

Is there a better way to do this. How can I bring the value out of [""]

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If the string had more keys , is there a way to dynamically create columns. Seems like bag_unpack does it but I cannot use those in query such as filtering with where.

{"Phish":["Spoof external domain"],"Spam":["Mixed analysis detection"]}