Answer: Oil Shortages
When you have grown up a long time and you return to things in your childhood, You often find yourself surprised at how small things are when you remember that they were so much bigger. The elementary school's halls look small, the old tree you used to climb doesn't really look that high, and toys seem small in your hands.
If you grew up playing with toys before the 1970s, there is one thing that can throw away your size-divergent nostalgia of: action figures. Today it is standard for action figures to be about 4 4 high; a size that is easily swallowed by an adult's hand, but which is still quite large for the children playing with them. Whether playing with G.I. Joe, Teenage Mutant Ninja Turtles, Batman, or any new toy brand on the market today, you will usually play with numbers below six inches in height.
Children who grew up in the 1960s and played with G.I. Joe, America's Movable Fighting Man, however, had a completely different experience. Then it was standard for action figures to stand tall 11 1/2 ″ long and pack clothes and accessories on an equal scale.
When the 1970s oil crisis put a significant share in the global oil trade and sent barrels of crude oil into the price, it also made it prohibitively expensive to hold out thousands of almost-foot-high action figures. Japanese toy company Takara struggled to keep its costs down and chose to release a reduced version of their popular Henshin Cyborg-1 line (a toy based on the GI Joe-led design that the company licensed from Hasbro, but with a cyborg  The smaller size toy, called Microman, was very popular – partly thanks to the backstory which claimed that the relatively small 3.75 ″ toys were actually the 1: 1 scale and the "Micromen" was from a planet populated by small people. The news in the story aside, other toy companies noted the fact that children seemed completely unwrapped by toys that were about 1/3 the size of the ones they were used to and quickly began to produce smaller action figures.