the case you mention is more of a hacker feat because that exploit had to be crafted specifically for facebook. meanwhile in this case it was most probably someone who just continuously scans the IPv4 address space for open mongo instances and applies the same generic "exploit" against them if it finds some in a fully automatized process
The terms get clouded a bit - but in my definition a "script kiddie" is pretty much this: someone with not much skill(like a kid), but hands on some hacker tools/scripts - to find easy targets and feel powerful. And later on, try to make some money.
And they can make great effort in doing so - but they remain script kiddies. They don't really know how to hack.
Whether this was just a "script kiddie", I doubt. More a professional ransomware gang. But what op probably meant was, it was not a targeted attack.
Other than that, it's commendable that you have working backups and are responding calmly and with a plan. I hope you get everything back in working order smoothly :)
[0] https://www.theverge.com/2016/3/8/11179926/facebook-account-...