Hell, you only have to look at the success of games like Fate/Grand Order to see why game companies will shit out a half baked mobile game. There's so much money in it, I think I saw a study saying mobile gaming makes up like 55% of the revenue in the gaming industry.
edit: not to say all mobile games are shit and half baked, there's some excellent games out there, I just don't think COD Mobile is exactly a labour of love.