It's more likely that sites became better at supporting mobile browsers and mobile browsers just became better in general.
This all leads to a better mobile browsing experience, javascript runs better on mobiles now, and site developers have learned what works and what doesn't, sites aren't Flash sponges anymore (which was the case even for sites with Mobile support 5 years ago), HTML5 and other W3C standards have taken off, the mobile screens even on low-end devices are usually similar to desktop/laptop screens in resolution.
People rarely care about their privacy, they auto accept pretty much anything that an app requests, Apple's lockdown of the permissions might help that case a bit, but again not because of privacy but because of the hassle of having to go into the settings and enable individual access for apps, this doesn't make people care for their privacy just annoyed and can't be bothered.
Content distribution and companion apps made sense when you needed to go mobile 5 years ago, when redoing your entire site to support mobile was too expensive and even then it wouldn't be a good experience due to how poor mobile browsers performed back then.
Now it makes absolutely no sense, it's another thing you need to support and worry about which costs money, it's much harder to make people download an app than press a link, and in the current "link-content-sharing" (e.g. outbrain) eco systems most sites operate in it makes very little sense since allot of the traffic is generated by those click-baity "25 reasons why Node is now considered harmful" links you have at the bottom of each TechCrunch article.
And on top of that even a low-end phone will usually have a 1080p(or close enough) screen, 2GB of RAM (unless it's an Iphone ;)) and a quad/hex core CPU which is more than capable of running pretty much any browser served content today mobile or not.
This is true at the layer of "why mobile browsers are capable of competing and beating app usage today"... the ante to get in the game...
But, the reason people are using browsers more than apps is simply because search is becoming the main use case of a smartphone.
I never look for an app on my phone beyond my home screen anymore, I just search or voice search my phone and expect it to either direct me to an app on my phone, or a search results page in Google.
I dont care where the solution to my need lives, I just want the quickest, easiest access to that solution.
Could also be the case, tho it's a bit hard to tell since you don't know how they've accessed the content, however if mobile browser would blow like they did only a handful of years ago that wouldn't be a viable approach.
Content access apps like TapTalk are pretty much dead, the only big community i know that still cares about their app is XDA-Developers which well is a very niche community to begin with.
Content distribution and companion apps made sense when you needed to go mobile 5 years ago, when redoing your entire site to support mobile was too expensive and even then it wouldn't be a good experience due to how poor mobile browsers performed back then. Now it makes absolutely no sense, it's another thing you need to support and worry about which costs money, it's much harder to make people download an app than press a link, and in the current "link-content-sharing" (e.g. outbrain) eco systems most sites operate in it makes very little sense since allot of the traffic is generated by those click-baity "25 reasons why Node is now considered harmful" links you have at the bottom of each TechCrunch article. And on top of that even a low-end phone will usually have a 1080p(or close enough) screen, 2GB of RAM (unless it's an Iphone ;)) and a quad/hex core CPU which is more than capable of running pretty much any browser served content today mobile or not.