As time has demonstrated dozens of times, platforms, behaviors and manias come an go in regular (though not quite predictable) bursts.
Betting that nothing ever changes is not consistent with the general arc of developments in the broader technology space.
Actually the opposite is likely true. The digital landscape is very "disruptable" and relies on various dark patterns (oligopolies, user illiteracy) to lock-in some "stability".
The individual events you mention are not the flood, they are the thunder indicating a thunderstorm is brewing.
I'm not saying things don't change because it'd be dumb to believe that given known human history. However I just despise the fact that even here in HN, any event happening in corporate that's otherwise minor outside of these doors is confidently defined as the tipping point ("fastest suicide" is maybe one of the most dramatic ways) and the company will go bust. Just wanted to clarify that, I agree with your sentiment.
The other major difference is content. On WA you only care about the content your direct friends/family create, on Reddit the masses are dependent on a few to submit comment (and even comment, there are a ton of lurkers who never comment, might not even up/down vote). If WA content goes to shit you can tell your BIL to stop sending you crap, if Reddit content goes to shit (due to loss of power users or moderation) it's a much harder problem to solve.
The WA exodus always struck me as way too difficult, getting friends/family to switch messaging platforms is super hard. Reddit? Might be unlikely but I was in the Digg->Reddit migration and I'm 100% looking for where I want to move now that Reddit is acting this way.
It's just the same cycle over and over. As time has demonstrated dozens of times, HN isn't good at forecasting nor is representative at all of most end-users. The great majority of Reddit users (and this doesn't include me) use the official app or the official website and therefore besides this very short protest which will end soon as like many other protests in the past for different reasons, Reddit will just continue to be as popular.