If the campaign died in a month, why is it consistently among the most-played games on Game Pass and on Xbox? It's 15th worldwide on Series consoles, above even Destiny 2. Halo Infinite overall has rarely left the top 20-25 of most played games across Xbox since launch. So, no, the game is very much not dead. Just because it isn't as popular on steam doesn't mean it isn't one of the most played games on Xbox.
If Halo is dead, Hi-Fi Rush must be also? Halo has stayed amongst the most played games. Has not gone anywhere. It can't be all that dead if countless other games have come and gone whereas it's still so heavily played.