Symbolic AI and ML/DL AI are two entirely different technologies with different capabilities and applications, that both happen to be called "AI" for mostly cultural reasons. The success of one is probably unrelated to the success or failure of another. In most ways, symbolic AI has "faded" simply in that we now take most of its capabilities for granted; e.g., it never strikes you as odd that Google Maps can use your phone CPU to instantly plot a course for a cross-country roadtrip if you so desire, but that sort of thing was a major research project way back when.

In contrast, ML/DL AI is still shiny and new and we have a much less clear grasp of what its ultimate capabilities are, which makes it a ripe target for research.