Delete Contact Trigger after insert failing

Question

I wrote a really simple trigger on Contact After Insert which isn't working as expected. The expected behaviour would be to delete contacts created from Leads converted that had the field Account_to_be_converted_in__c populated.

public class TriggerContactDeleteFarmingContacts implements Triggers.Handler {
    public void handle () {
        List<id> ContactsToDelete = new List<id> ();
        Map<id,Contact> Mapcontacts= new Map<id,Contact> ();
        for(Contact C: (List <Contact>) Trigger.new) {
            Mapcontacts.put(C.id,C);
        }
        System.debug('Mapcontacts: ' + MapContacts);
        for(Lead L: [SELECT Account_to_be_converted_in__c,ConvertedContactid FROM Lead WHERE isConverted = True AND ConvertedContactid in: MapContacts.keySet()]) {
            if(MapContacts.keyset().contains(L.ConvertedContactid) && !String.isBlank(L.Account_to_be_converted_in__c)) {
                ContactsToDelete.add(L.ConvertedContactId);
            }   
        }
        Database.delete(ContactsToDelete);
    }
}

For some reason I still don't see the query isn't returning any row, but if I do it on query editor it returns the expected results.

EDIT: (Using on Lead After update Trigger)

public class TriggerLeadDeleteContactonConvert implements Triggers.Handler {
    public void handle () {
        Map <id,Lead> MapOldLeads = (Map<id,Lead>) Trigger.oldMap;
        List <id> contactsToDelete = new List <id> ();
        for(Lead L:(List <Lead>) Trigger.new) {
            if(L.isConverted != MapOldLeads.get(L.id).isConverted && !String.isBlank(L.Account_to_be_converted_in__c)) {
                contactsToDelete.add(L.ConvertedContactId);
            }
        }
        Database.delete(contactsToDelete);
    }
}

If I try the code above I'm getting this error :

ENTITY_IS_DELETED

So the conversion isn't possible to be achieved.

EDIT 2: (Using Trigger on Lead After Update without using Id but List, still getting same error)

public void handle () {
    Map <id,Lead> MapOldLeads = (Map<id,Lead>) Trigger.oldMap;
    List <Contact> contactsToDelete = new List <Contact> ();
    for(Lead L:(List <Lead>) Trigger.new) {            
        if(L.isConverted != MapOldLeads.get(L.id).isConverted && !String.isBlank(L.Account_to_be_converted_in__c)) {
            contactsToDelete.add(new Contact(id=L.ConvertedContactId));
        }
    }
    delete contactsToDelete;
}

Answer 1

This is due to when this contact is converted you lead is not converted thats why you are not getting any records. Due to this you need to use Lead afterupdate trigger.

Lead conversion order of execution

Account Before                 (Fires based on lead settings)
Account After
Contact Before                 (Fires based on lead settings)
Contact After
Opportunity Before             (Fires based on lead settings)
Opportunity After              (OCR's not available)
Lead Before
Lead After                     (OCR's available)

Reference 1