GaaS is massively risky, and if you try to play it safe (aka like HYENAS) then by time you release your game, the thing you were copying is either dead itself or so entrenched that either way you look at it, your game is gonna fail.
Live service games are high risk and high reward, but you actually have to make something interesting and original to even have a hope of raking in billions.
I can really only think of a few instances where someone completely ripped something else off and cashed in bigger. Fortnite is the main one that springs to mind, but even then Epic did it in a way that made BR games more appealing to kids.
Fortnite BR also released
extremely fast, only a few months after PUBG released if my googling isright. They could still get in while the genre was still taking off.
And yeah, GaaS in general is brutal. You can't be chasing trends, you need to be
setting trends and this is difficult. Or, if you are chasing, you need to have a sufficiently appealing differentiator and even then still can't take to long to release unless you already have existing clout (i.e Warzone has Call of Duty pull) or the existing offerings will be too entrenched. And of course it will also have to be good.
For Example for Battle Royales PUBG was March 2017, Fortnite BR was July 2017 and Apex was February 2019.
The current dev cycles of 5+ years are just way too long for this.
It's why I'm presonally really curious what's going to happen to the upcoming Genshin-likes. It's been 3 years since Genshin and the first competitor is probably next year. That's a lot of time Genshin had to solidify its position (like, personally I just can't see myself dropping it at this point, I'm too invested in the world, story, lore and characters)), but there are no "2nd and 3rd place" in that particular market yet.