Why the fuck is he helping them? They literally said it themselves there's no need for a newspaper Club anymore when they already have a club that's in charge of a official School YouTube channel that posts updates.
Like others have said, it's for pragmatic reasons. You know the saying "keep your friends close, keep your enemies closer"? It's something like that. Even if the newspaper club gets disbanded, they'll just make a "society" (essentially a hobby group that's a pseudo-club, but is given minimal support by the school) and keep chasing scoops. Both out of their sincere- if disturbing- passion for newspaper, but also out of desperation to become a proper club again.
And in that ravenous hunt for school scoops, they will inevitably go for gossip and scandal. Meaning sooner or later they'll sniff out something going on between the MC and the twins, and eventually their throuple relationship will get outed and their social lives ruined by the scandal and controversy. So while it would be easier and entirely justified to do nothing, their options are "
Let the club get disbanded, then spend the rest of our school years watching our backs for paparazzi and gossip-mongers."
OR
"
Help the club remain active by making them a legitimate and informative school newspaper again, so they no longer have the need nor desire to hunt for scandals."
Bonus: they will owe the MC and the twins
big time for helping save the club, and it's entirely possible the one sister actually starts enjoying the club and sticks around as a proper member. They wouldn't dare turn on their savior or throw one of their club members under the bus after all of the help, after all.
So like I said: keep your friends close, keep your enemies closer.