An influential figure in the later development of general relativity was John Archibald Wheeler (1911-2008). In the academic year 1952/53 he offered a yearlong course on special and general relativity at Princeton (the first such course there). According to Paul Halpern's book cited below, ``among the highlights of the spring session was a class trip on May 16 to Einstein's house (...). There, the eight graduate students in attendance had the unprecedented chance to ask the theory's designer any questions on their minds." Here are some of Wheeler's papers on general relativity from mid- to late 1950s (the actual list may be longer if he published something in physics journals that were not covered by Mathematical Reviews):
MR0127375 Wheeler, J. A. Neutrinos, gravitation and geometry. 1959 Rend. Scuola Internaz. Fis. "Enrico Fermi'', Corso XI pp. 67–196 Zanichelli, Bologna
MR0100507 Weber, Joseph; Wheeler, John A. Reality of the cylindrical gravitational waves of Einstein and Rosen. Rev. Mod. Phys. 29 1957 509–515.
MR0094239 Lindquist, Richard W.; Wheeler, John A. Dynamics of a lattice universe by the Schwarzschild-cell method. Rev. Mod. Phys. 29 1957 432–443.
MR0093387 Misner, Charles W.; Wheeler, John A. Classical physics as geometry: Gravitation, electromagnetism, unquantized charge, and mass as properties of curved empty space. Ann. Physics 2 (1957), 525–603.
MR0091832 Regge, Tullio; Wheeler, John A. Stability of a Schwarzschild singularity. Phys. Rev. (2) 108 (1957), 1063–1069.
MR0091828 Brill, Dieter R.; Wheeler, John A. Interaction of neutrinos and gravitational fields. Rev. Mod. Phys. 29 (1957), 465–479.
MR0090447 Power, Edwin A.; Wheeler, John A. Thermal geons. Rev. Mod. Phys. 29 (1957), 480–495.
MR0067622 Wheeler, John Archibald Geons. Phys. Rev. (2) 97, (1955). 511–536.
- Kruskal's paper mentioned in the comments was written up and submitted on his behalf by Wheeler.
- While it might be difficult to attribute the increase in interest in general relativity to a single paper, there was an important event that influenced later developments. In 1957, a conference on general relativity later known as GR1 was organized by Bryce DeWitt and Cecile Morette DeWitt. According to the report by Peter Bergmann (one of participants) in Reviews of Modern Physics, https://journals.aps.org/rmp/abstract/10.1103/RevModPhys.29.352, one of main inspirations was a quest for developing quantum theory of gravity (still elusive). A readable account can be found in "The quantum labyrinth. How Richard Feynman and John Wheeler revolutionized time and reality." by Paul Halpern (Basic Books, New York, 2017) and in Feynman's own memoirs.
- The history of general relativity seems to have followed a more complex path than the `beginning-to-slump-to-golden age' scheme, according to Hubert Goenner in his paper "A golden age of general relativity? Some remarks on the history of general relativity." It is available here: https://arxiv.org/pdf/1607.03319.pdf Some developments and statistics from 1950s that he lists do not seem to support the thesis of there having been ``hardly any paper published" in this decade.