Another reason USSR (Soviet Union) was silent is that they were against the idea of manned lunar exploration in the first place. Better to have robots do they job, as they subsequently proved.
[quote[Russia may likely have planned to fake their manned moon flights too. Aboard Zond 5 was an audio cassette player which played back the voices of cosmonauts Pavel Popevich and Vitali Sevastyanov. At the time many thought Russia had sent the first men around the moon, but upon return of the capsule it was revealed that it was only a tape recording. NASA, who at the time weren’t officially planning a ‘manned’ moon mission until April or May 1969, responded to the tape recorder stunt by changing Apollo 8’s flight plan from a high earth orbit flight to a lunar orbit flight in December 1968. [/quote]