Endgame 2.3 Avengers collect all stone but Thanos knows everything.

As we know, Avengers had already collected 5 stone from different timeline so only one stone was left. Let talk about how they collect Power stone.

6) Power stone : James Rhodes and Nebula went to 2/14 timeline where starload was already there for same purpose . Nebula make him unconscious and take power stone from which causes serious damage to her hand. As they already got stone , James Rhodes came s to original timeline but when Nebula tried to do same thing , because of ger past memory she fell down there .

As all stones already collected , but Nebula fell off the ground ,Thanos of 2014 timeline get to know about this and captured her. Since Nebula wss  humanoid meaning half humans and half Android ,Thanos scan her memory and know about everything. Thanos knew that by 2019 ,he will be able to collect all six stone and wipe out half of living form from the universe. So , Thanos gets more confident that he will be successful anyway as future can't be changed.