One which I had heard many times, yet never really understood until last night.
He'd always been like that, not fully understanding things until much later, if then.
He hadn't understood until that moment how much she meant to him.
She "never understood until too late what they meant to do"!
But I never understood until today why you disappeared from things so suddenly.
These effects did not begin to be understood until Newton's time.
No one to understand, until they met each other.
"I did not understand the concept of ambush until too late."
He did not understand its meaning until years later.
He saw them, but didn't understand until too late.