Wherever the bots come from, they are well established
Many of these accounts are just bots. China, Russia, India, Pakistan, Bangladesh make plenty, as no doubt do other nations.
Instagram bots sell for about 0.78cent I am informed. It's called SMM panel reselling. These bots are found on many platforms. The older the bot, the more validity it has, because panels regularly conduct searches and erase bots, don't they. So if it survived a few years its vote, comment, like etc. looks more real.
USA Today cleaned up its Twitter followers a few years ago and found that 1 million of the 8 million were bots.
Facebook cleaned 1.3 billion bots and fake accounts during Q1 of 2021, down from 1.7 billion in Q1 of 2020. 1.7 billion were removed /cleaned up during Q4 of 2021.
https://www.statista.com/statistics/1013474/facebook-fake-account-removal-quarter/
Not only the panel activity, but the activity of search engines endlessly visiting the pages, wastes electricity and datacentre space.
There are also zombie accounts, real people's accounts pwned, some exacerbated by the fact that what would be visible on a desktop is not visible on a phone app. The real user keeps using it unknowing that something has been added.
Some panels have taken steps to require proof of identity on opening an account.