The problem is the lack of a "backyard" ICBM program to piggyback off of... the R-7 that the sputnik launcher was based on "was designed with excess thrust sinc

The problem is the lack of a "backyard" ICBM program to piggyback off of... the R-7 that the sputnik launcher was based on "was designed with excess thrust since they were unsure how heavy the hydrogen bomb payload would be" (wikipedia.)