On what basis do you conclude that CL's mother was "domineering" because "she had married more than once".
By extension of that argument you would have to conclude that ALL women who married more than once would have to be domineering, and that doesn't seem to be a particularly sensible line of reasoning.
I do not conclude that at all.
It is an idea of Fisherman.
Here it is (he is talking about himself in third person here):
What Fisherman says is that many serialists have a background involving an absent father and a domineering mother.
Then Fisherman points to how Charles Lechmere had a lacking father figure, who left the family when Charles was but an infant - or perhaps even before he was born.
After that, Fisherman notices how Maria Louisa, Lechmeres mother changed jobs a number of times and married on three occasions, two of them seemingly bigamously, and how she somehow worked out a solution with Charles where she had one of his daughters staying with her. At that stage, Fisherman thought "Wow, that seems to be one resourceful woman"!
Fisherman then thought about how nobody got killed as long as Lechmere was living in close geographical proximity to his mother, whereas the murders started once he moved away from her.
Now, being the seasoned crusader that Fisherman is, he would NOT say that it iss a proven thing that Charles must have been swayed by his fathers absense to become a killer. Nor would he say that it is a proven thing that Lechmere´s mother WAS domineering.
He would only say: Absent father figure. SEEMINGLY resourceful mother, possibly domineering. On the surface a good fit for the sort of background many serialists have. End of.