According to Angela Canepa, the texts were necessary to show the systematic way the Wagner family dealt with the wives/partners of Jake and GW4. When they pressured the women, forcing them to leave, they all worked together as a unit to help get rid of the former partner and take control of the child or children.
The family works as a unit on these matters. Just as Jake helped GW4 abuse, threaten and chase Tabitha away, GW4 would do the same for Jake. The texts showed how the violence, psychological abuse, etc. came to involve threats to Hanna that were similar to the threats made to Tabitha. False claims of not taking care of the child properly or that someone is molesting the child. Trying to make the mother look unfit, neglectful. Demanding that the child live "with the family", etc. Also "you're not loyal to my family, you treat my mother/father/brother badly". Physical punishment if family is disprespected (Hanna getting slapped around).
It's a family cult, it really is. All for One and One for All