Why am I getting a privilege error when creating a table from a trigger in Oracle? [duplicate]

Question

I'm trying to create a trigger that creates a backup of a table before it is truncated. However, I'm getting a permission error when attempting to create a new table. Why?

create or replace trigger my_trigger
before truncate on schema
begin
    if (ora_dict_obj_type = 'TABLE' and ora_dict_obj_name = 'TABLE1') then
        execute immediate 'create table TABLE1_BACKUP as select * from TABLE1';
    end if;
end;
/

I get this error:

ORA-04088: error during execution of trigger 'MY_SCHEMA.MY_TRIGGER'
ORA-00604: error occurred at recursive SQL level 1
ORA-01031: insufficient privileges
ORA-06512: at line 3
04088. 00000 -  "error during execution of trigger '%s.%s'"
*Cause:    A runtime error occurred during execution of a trigger.
*Action:   Check the triggers which were involved in the operation.

Running this PL/SQL outside of the trigger works just fine:

begin
    execute immediate 'create table TABLE1_BACKUP as select * from TABLE1';
end;
/