The problem is that massive companies know exactly what to do to stay massive.
They have endless advertising and make sure that their products are for sale everywhere (undercutting the competition or cutting 'special exclusive deals' with retailers if necessary) - to the extent that most people either don't really think about there being an alternative or stay in the mindset that this is 'normal' chocolate and the expensive stuff (invariably from independents or very small specialist companies) is a rare treat - rather than thinking that maybe chocolate should be a treat and savoured rather than being shovelled down (not judging at all - I need to grasp this lesson as much as everybody else).
I'll never for the life of me understand why huge companies spend so much money on blanket advertising rather than just spending the same money on making much better products and gaining lifelong happy customers.
However, this is precisely the MO of big companies nowadays (with a very few notable exceptions): they rely on people's inertia and couldn't care less how happy you are with them as long as you never get unhappy enough to leave them. In fact, if they knew that their customers were utterly delighted instead of just grudgingly willing to stay clinging on, they'd probably assume that they must be spending too much money somewhere that could be cut back to boost their profits even further.
They'll outright boast on high about having a 90% customer 'satisfaction' rating (i.e. people aren't brave enough to leave them or don't understand that there are much better alternatives as 'bigger must be better', right?)
Even if that 'satisfaction' rating wasn't just an inertia thing and genuinely represented true delight (which it really doesn't) - if I owned a company with those ratings, I'd be horrified that 1 customer in every 10 wasn't happy with my products. You'll always get a tiny minority of people who moan about anything and expect the Moon on a stick for a pound - but 10% unhappy customers is appalling - not something to boast about!!
Take broadband providers for example. How many people grumble about shocking reliability and customer service and yet keep switching between 4 or 5 big providers (and keep grumbling). Look at ISPReview.com (which, of course, is subject to bias and reviewers are self-selecting, but which should in theory cover people knowledgeable and interested enough to actually seek out the site in the first place), and see the 50 best rated ISPs. Apart from possibly Zen (currently at 12), the first provider that the vast majority of people would ever even have heard of is rated the 20th best - yet they have probably 20% or so of the entire UK customer base, as do those at positions 30, 32 & 34.
The exact same is true of the handful of 'big boy' gas and electricity providers.
Sadly, most of us are happy to be gaslighted into believing that what we're told is the best (by the huge brands selling it) must actually be the best and/or are too scared to give anybody else a look in - and we all have a tendency to follow the crowd blindly. At least, that's the only reason I can possibly think of why Subway is still in business in towns that have nearby independent sandwich shops with much greater quality and far lower prices.
Sorry - bit of a rant there!