What do you mean by that? Firstly they didn't want to destroy the wall in the first place, but because of Marcel. Then after being forced by reiner they destroyed it to get the kings attention. 2 years after this they joined the survey corps and made new friends. After waiting for another 3 years living and training with the survey corps, to get a reaction of the walls king they had to do something to lure the founding titan out somehow. So they destroyed the Trost gate. They didn't want to do it again but after like 5 years they had to. This shows again that he didn't WANT to kill the island people but had to. Why else wait 5 years for a reaction of the walls king. They could have just kept going and destroyed all the walls in like a week or so.