They did not do any useful work until BTC were used for real transactions.
Any transaction in the Bitcoin-network is a real transaction.
Without that work, not a single transaction would be possible, so BTC could have never been used, ever.
That's the thing you guys don't get,
the process called mining is not about generating, or distributing coins, it's about making transactions possible and secure.
He's also assuming that they somehow got rich doing that work, which is also untrue.
They either hold thin air valued at around 27 USD, or have sold their thin air for something more than 0 USD, so that's an infinite % profit on useless busywork.
As stated a couple of times now, it's not useless work, it's work that keeps the system running.
It's work needed to be done by someone.
No work == No transactions == No payment system == No nothing.
Again, do some research to learn how Bitcoin works.