I like Arlo, and as someone who's trying to get into content creation later this summer, I get it, I really do, this was an algorithm video. He very much disliked the first one, he doesn't care about Sonic at all in the first place, and most of all, it's a kids movie with kids movie humor that was never going to mix with (from what I can see) Arlo's constant want for things to take themselves super seriously and be big and bold all the time.
But yeah, let's not beat around the bush here, he did this because it's easy views from a fanbase that is the easiest bear in the world to poke and feeds an algorithm that's Sonic heavy ATM.
Basically: Sonic fans are the targeted demographic for the Sonic movie, and anyone outside of that will probably be whelmed. Shocking, I know.