For member or full member accounts, I can understand since it's easy to get merit to rank up to that level. But for Hero/Legendary, yeah I don't get why they throw away such accounts and reputations for weekly payment from a scam campaign like 1xbit. I suspect most of those accounts are alts or multi account or already have a low reputation already.
That means they can anytime ditch that account for another or give merit to rank up a new account.
The merit system we currently have it is actually quite recent in comparison to the age of the forum itself. The merit system started in 2018, I think. Before the merit system implementation, users could rank up to Hero/Legendary rank just by accumulating activity (participating during enough months in a consistent way).
When the merit system got implemented those who already had rank earned by activity received "airdropped merit", Hero Members received 500 merits and Legendaries Received 1000 free merits. This means that today in order to have a Legendary account to throw away by joining 1xbit, that account just needed to have activity and be old enough to have received free merits in 2018.