Adding transition at the begining

[yearmfew]

I have a project that includes d3-networks of users. User can choose the network from a dropdown menu.
When user change the network, it comes with some kind of fluctuation and it disturbs the user.
I have tried to solve it gsap transitions and transitions of vue.js but it comes always with fluctioation and then happens my transition which seems worse than normal.
You can have a look to my project:
https://github.com/MethodJules/concept_map_tool

Develop branch is the actual branch.

How can I solve this problem and add some kind transitions. Both at the opening of the page and when user change the network