They get more views with tags related to cakes, baking, pizza, loving cooking, family mealtime, etc. Nothing more than that, it's just ways to maximise views/evidence their 'reach' and therefore improve their marketability to companies.
They may have a genuinely healthy, balanced diet with a relaxed attitude towards calorifically dense foods that enables them to effortlessly maintain their body shape and looks (and let's face it, they're already winners in genetics by and large to be deemed attractive enough to be famous/influencers, so being able to do that without much worry is reasonable). They might actually live on fuck all other than junk and appetite suppressants. The cakes might never pass their lips and go straight into the bin without suitably photogenic people to be filmed eating them. They may do this because it makes them money and then engage in ED behaviours to mitigate the effects outside shoots.
Whatever the reality is, they've decided, often with advice, that they stand to make the most money from those foods rather than going for the slightly more niche subject of meal prep/resistance training/health nutrition. Especially if their target audience is, for example, the affluent twenty something female consumer, going on to the affluent early 30s mums (add in Christian if it's the American demographic they're targeting) or the twenty something mum of a toddler in the UK where the influencer wants them to identify with her ready for a collaboration with B&M or something.
It's about money. And the sort of money some of those people can pull in from a quintuple chocolotta ten tier cake/etc is more than they can make from multiple tubs of Salmon, rice and broccoli with chicken breast to mix things up a bit from time to time - especially when the latter will also benefit from a considerably more athletic lifestyle so their body is the product as much as the surroundings.