While we can lambast our players (Bastoni, Sommer, Asllani and maybe others) for not positioning well and not clearing the ball, let us also not forget that they were playing against a well oiled machine. Most of the Real Sociedad players have played together since they were youngsters and their coach, Barrenetxea, was also their coach back then.
This was a result of multiple years playing together, knowing when to run forward to snatch the ball. Apparently not the first time they scored a goal from that kind of pressure.