Advantages for the manager:
Targeting different categories of investors (multipliers allow to offer an investor several accounts of one manager with different levels of profitability and risk);
There is no need to create several accounts with different levels of aggressiveness (each subsequent multiplier increases the aggressiveness of trading on the account. For example, an account with a multiplier of "2" is twice as aggressive as the Master account; the aggressiveness of trading on an account with a multiplier of "4" is twice as much as the aggressiveness on an account with a multiplier of "2" and four times as much as on the Master account);
Transactions are executed on all multi-MA accounts at a single price (in order to achieve execution at a single price on all multi-copy accounts and avoid discrepancies, all open orders are aggregated beforehand and only then are transferred to external counterparties. This would not be possible if a manager opened each account and orders manually).