Liverpool defeat last night in the semifinals was quite surprising considering they were playing at home and what they have shown so far in the English league, but because there is still a second leg so the chance to qualify for the final is still very possible to achieve besides the aggregate is very thin so I am very sure the red will take revenge on Tottenham in the second leg later. Arne just needs to improve the mentality of his players, that is what is really needed in this crucial match.
There is one thing I have notice with teams in one short competition, the competitions looks like one time thing. So the teams involved especially the ones that don't have a good place in their domestic leagues don't play down in this leagues, they put effort like it's their last chance to make something out for the season which is why you see teams you don't expect doing something good for their self in such leagues, Tottenham didn't come to play with Liverpool.
Another factor is tiredness, team that is in their domestic league trying so hard to keep the place will likely be tired than a team that is just looking out for their place in the table, Tottenham is very energetic plus the fact that they are playing at home while Liverpool is their guest, each player didn't downplay their role in that match and that paves way for their success despite the push, the shorts on target and the big chances created by Liverpool.