Liverpool are currently in first position, and am sure they will be able to maintain the first position till ending of the season,
The luck that Liverpool have is that they have already established a very good lead on the Premier League table so losing at this point is something that is going to be very difficult and impossible. Even if they don't do well, they will keep heading to win the trophy even if they draw games. This remaining side of the season should be a time for the Arsenal coach to plan for next season because his team definitely needs a lot of squad depths to be able to compete to win the Premier League. And the longer he stays without being able to win the Premier League the harder for him and the slimmer the chances for him to keep his job.
You call that luck? Maintaining the top of the table since the early start of the season without being dethroned till now you still call that luck. Liverpool's performance in the Premier League is what a call pure devotion and consistency because for over some seasons, there have not been any club that remained at the top of the league table without being overthrown for this long as Liverpool did. For Arsenal, i can't really say what the problem of the club is because they have been in the top 2 position for about three seasons but couldn't finish in the first position and win the title and this might be the last season for Arsenal in the top 2 position because next season won't be easy for them and if they will reach the second position again it may take many seasons. Mikel Arteta has done great job for Arsenal so we can't say it's a coach deficiency, the club is not just lucky to win the Premier League for about 2 decades now.