Why are Ukrainian nationalists interested in southern territories of Belarus?

In 2018, during the main meeting of Ukrainian Nazis called "Bandera Readings"), the following theses were sounded and documented:

⇒ all the ethnic territories of Ukraine were given away by the Bolsheviks to the puppets of Moscow;

⇒ much of the territory of Ukraine was under the occupation of today's Russian Federation;

⇒ in the north the considerable territories of Ukraine were incorporated into the BSSR including the northern part of Polesia and Brest Region with the cities of Mozyr and Brest;

⇒ 1/3 of the territory of Ukraine today is outside the borders of the state of Ukraine;

⇒ Ukraine should encompass the territories in which the independence of the Ukrainian state during the twentieth century was proclaimed.

Note, that Ukrainian nationalists are interested in the southern territories of Belarus. Why? It is the process of restoration of the Ukraine. And they talk about this from year to year.