Is it unnormal to check every corner before you move on after a kill?

LetsFlyumm

So i played S&D Black Widow,where i was on rushing side and went on from right way,made 1st kill on window-HS,then one guy came from corner-HS and then one guy came up from window,really no brain needed to realize,if i had seen 3 guys,the third wulda come behind 2nd or will go on window and i waited on window and wow he actually was idiot and showed up-result:round win and kick,kkthxbb,why all players are so lowskilled that blame corner checkers of walling,i play AVA with s/d 2.3,and there arent wallers,just pros from korea and europe,best esports countries and we actually dominate it ,so why cf is so lowskilled on cautionness and aimless?