As soon as you tell your first wife you want to marry a second they get extremely jealous and insecure and demand divorce
"Am I not good enough"
"You dont love me anymore;"
"Wixi cusub aya la jecel"
Etc etc. So i dont blame these men who want to keep their family intact
Why tell her after you marry her? Why not tell her before the nikah "listen up abaayo, I may consider a second wife" and let her decide.
A lot of you lie to a woman about only wanting one wife and then when she's got stretch marks from carrying your big headed babies; you want a second wife.
Be a man, be upfront.