Dear Nostriches. Please help to share your knowledge and wisdom to me

I'm trying to understand this chart.

I understand that paper money value should go down as more of it is being printed. simply more money chasing the same amount of good

-so I understand if dollar value decreased post 1971 because it became fiat and can be printed freely

-I kinda understand its value goes down after bretton woods agreement, as it may actually being printed more than the amount of gold reserve the fed have

-but I don't understand what is causing the sharp drop soon after the fed is created? does anyone know what happen there? link to sources of the history lesson will be really appreciated. will send some zap, not much but its a zap :D