Take the dominance of French players during the 1920s–1930s. It was largely due to restricted international participation. Ask yourself why the last time a French player won the French Open singles title was back in '83. It wasn’t until the 1960s that the French Open became a truly 'global' event. And as soon as that happened, you either had Spaniards, Swedes, Aussies winning everything. (It actually started sooner, back in the '40s). Either way, French players were basically just playing against each other.
Same thing with Wimbledon.
You essentially had Brits playing against each other for over 50+ years and occasionally Aussies and Kiwis. (No wonder—they share historical and constitutional ties with the United Kingdom as part of the Commonwealth of Nations, i.e., an organization of countries that were mostly former territories of the British Empire.) Then it's only after WW1 that "international" players started to show up (French, Americans), and it was game over for the Brits when the Open Era started in '68. The only exception was Andy Murray, who won it twice in 2013 and 2016. Twice since 1968. Only twice in the span of the last 56 years.
