Crashjean surviving this season is quite a surprise, and Magnussen isn't exactly known as a pleasant person to meet on the asphalt either.
Well he had an horrendous start with 0pt after 8 races but when you look at the ranking starting from Austria in F1.5 it looks like that
Perez 45pts
Ocon 38pts
Grosjean 37pts
Hulkenberg 35pts
Magnussen 29pts
Leclerc 28pts
Sainz 25pts
Alonso 18pts
Not to mention Grosjean was disqualified from 6th in Italy and outqualified Magnussen in 8 of the last 9 races.
Now his start was atrocious no arguing (besides Australia), but if he was to get replaced who was available for Haas mid-season? Maybe they could've taken Ocon at some point but I don't think they were keen on the idea, otherwise I'm not sure who was available and they were willing to take (maybe some FE top driver?)
I think it also makes it clear what was overall the ranking in cars overall after the start of the season where McLaren and Renault took a lot of points on the midfield.