If their surveillance was legal and within the scope of their charter I can understand how they don't want their methods and sources revealed.
The question is did these foreign governments step outside the bounds of what is legal.
If they did should President Trump release the information and expose and embarrass these foreign governments?
If he did what kind of long term riff would it cause between our governments?
Retaliation could be brutal.
The reason is probably a little bit of both.
Illegal and embarrassing...............