They are still leading the match with a 1 goal advantage, this is not a definite guarantee that they will get 3 points at the end. Even after their quick goal early in the first half, they still couldn't get their second goal.
And based on the current match statistics, I am sure that Crystal Palace will have their goal, so, if Arsenal don't score their other goals, they will have to be satisfied with the 1 point that they will most likely get later.
An own goal from Henderson gave Arsenal a big lead against Crystal Palace at Emirate Stadium. I'm not surprised to see Arsenal with a 2-0 score against Crystal Palace in the first half because Arsenal will not want to drop another point today. If Arsenal finally wins against Crystal Palace today, Arsenal will close the gap with Liverpool at the top of the Premier League table.
Currently Arsenal is leading the match with a score of Arsenal 3 - Crystal Palace, Arsenal's third goal was scored by Leandro Trossard. I think I have to take back my previous words about Crystal Palace who will provide resistance by at least scoring 1 goal, they're like losers at Emirates Stadium.
The current score gap seems to be a cover that Arsenal will get 3 points at the end of the match and even though Arsenal is now getting closer to Manchester City & Liverpool, we have to remember that both teams still have a 1 match deficit.