MySQL trigger after insert with insert and delete instructions does not work properly
Your trigger tries to do something that cannot be done in MySQL. You cannot use an SQL statement (DELETE, in your case) on the table that is associated to the trigger. You will get an error like this:

ERROR 1442 (HY000): Can't update table 't' in stored function/trigger because it is already used by statement which invoked this stored function/trigger.


You are probably using MyISAM for your table. The DELETE does not cause a rollback, because the engine is not transactional. If you switch to InnoDB (which is usually the best choice) you will notice that the trigger and the original INSERT will completely fail.