"were well understood" is a correct and usable phrase in written English.
It is typically used to describe a state or condition of understanding something very clearly or thoroughly. Example: In his research paper, the author argued that the complexities of quantum mechanics were well understood by a select few scientists, but still remained a mystery to the majority of the population.
And these tools were well understood going into the crisis.
Two-dimensional manifolds were well understood by the mid-nineteenth century.
"But the processes used by Myriad to isolate DNA were well understood by geneticists," Justice Thomas wrote.
However, the difficult mathematics relating diffraction patterns to crystal structures were well understood, although the techniques for imaging crystallised biological molecules were still in their infancy.
By the end of the 60's, the foundations of molecular biology were well understood, and Dr. Crick was eager to go to his next great question.
Hospital hygiene reached its high point in the era when microorganisms were well understood but antibiotics had not yet been developed.
By David Remnick On the less desperate days of the first Palestinian uprising, fifteen years ago, the rules of theatrical engagement were well understood.
The great determining technologies electricity, the telephone, the internal combustion engine, even manned flight were the products of a previous century, and their applications were well understood.
On the less desperate days of the first Palestinian uprising, fifteen years ago, the rules of theatrical engagement were well understood.
In the end, senior NASA managers decided to take the time needed to make sure the problems were well understood and repaired before making another attempt.
Such problems caused by democracy are not new; they were well understood by the Greek philosopher Plato, who explained that democracy can make us overweight as well as adversely affecting the economy.
