I am wondering if this is something that other people think. It seems to me that during a period of time from the late 19th century to the early 20th, there are a large number of philosophers who were thought to be relatively influential in their time but whose influence has declined. The philosophers I am thinking of are Bergson, Spencer, Dewey, Santayana, James, Moore, Royce, Lotze, Russell,Peirce, Comte, Lewis, and Whitehead. Maybe I am just being biased since these were relatively recent? But it seems like there is a bit of a dead zone between the end of German idealist philosophy (with Schopenhauer, Nietzsche, and Marx) and contemporary philosophy (Heidegger, Wittgenstein, etc.).
One way to interpret "influence has declined" is that philosophers on the list were "superseded" by their successors, although "influence has transformed" seems more appropriate. Russell and Moore are the founders of analytic philosophy which still dominates the Anglophone countries. Comte is the founder of positivism, the logical positivism of the Vienna circle (Reichenbach, Carnap, Neurath) was partly inspired by him (along with Mach and Mill). Peirce, James and Dewey are the founders of philosophical pragmatism, which transformed into logical pragmatism (Glock's term) after merging with logical positivism in 1950s. Quine and Davidson are the more recent carriers of that mantle, and the late Wittgenstein helped. Bergson is an inspiration for existentialists, especially for Merleau-Ponty. However, Comte worked earlier than Marx and Nietzsche, Wittgenstein was Russell's younger contemporary and heir apparent, who ended up repudiating him like Aristotle Plato. Husserl rose to prominence at about the same period, and Heidegger was to him as Wittgenstein was to Russell. So I don't really see a gap.
If you want a gap look at the continental philosophy after 1950s. The big names, Merleau-Ponty, Sartre, Foucault, Derrida, Lacan, Deleuze, Badiou are all conspicuously French. Of course, there is Gadamer and the Frankfurt school, but that is a far cry from Kant, Hegel, Nietzsche, Husserl or Heidegger. Perhaps, Nazism in Germany and the flight of intellectuals left a lasting mark on German speaking philosophy.