Go ahead and map that out mathematically and let’s see if 4 billions year has been long enough.
If it took a million steps in a billion years, that would be one step, on average, every thousand years.
What would be the standard deviation on average "years between steps"? A million years? Who knows?
But, we have the advantage of knowing for certain that 4 billion years was plenty long enough for what actually happened.
What exactly that was we don't know in more than general outlines.
We do know much more today that George Wald did in 1954, which is the point of this discussion.