[robot_jesus]

Apart from the possible line items others have noted, it's also worth calling out that a ton of the paid media they're talking about is highly targeted digital media.

General awareness campaigns are not in vogue these days, especially for CPG companies. You're not seeing a lot of billboards or train wraps for these brands anymore. Instead, you're probably just not deemed by the all-knowing models to be a likely buyer (count yourself lucky--it's probably a good sign for your diet and health).

But it's not inconceivable at all that the $2B spend it invisible to a high portion or even a large majority of the population if they can get more ROAS by targeting specific subsets.

Edit: one more ps that I thought was funny. The one brand you called out (Kit Kat) is only owned by Hershey in the US so it's entirely possible that the online ads you've seen are actually Nestlé's, depending on what sites you're viewing and/or where you live.