This is a very common myth, there was never a period where everyone programmed in assembly and then high level languages were introduced.
Pretty much since the first CPUs were released, there were already programming languages for them.
Alan Turing went from hooking physical wires up, to writing Autocode for the Ferranti in less than a Decade.
And it's not even that the period of Assembly programming was brief, spanning almost a decade after WW2, the guys wrote in symbolic mathematical language before setting on to write the physical schematics of their machines.
So no, there wasn't a period where we all programmed in Assembly and then we discovered programming languages and we saw that it was good.