We saw a surprise in the EFL Cup semi-final match and it was very interesting and exciting. Arsenal lost the match and they are very likely to be eliminated from the semi-finals. Newcastle played strongly and with excitement which resulted in them achieving a good result to qualify for the final. Newcastle are two goals ahead in the first leg of the semi-final, of course they will be even stronger against Arsenal in the second leg to qualify for the final. I think Arsenal may not be able to score as many goals in the second leg so their chances of going to the final are also very low.
I think you a little bit underestimate Newcastle and if you look at the last games of Newcastle, you will see that the last 7 matches Newcastle won, and among the teams that Newcastle beat were Tottenham and Manchester United and Aston Villa and now Arsenal.
So if you look at the statistics, Newcastle should have been the favorite, because they have more wins than Arsenal, besides Isak has been playing at a great level lately and can not only create chances for teammates, but also score himself.
Besides, Newcastle defense plays almost without mistakes and Newcastle conceded only 2 goals for these 7 games and I do not remember such a game from Newcastle for a long time.