I have 2 Object, No relationship between obj - one field is common - My requirement is once i change fiedl value in 1 objject it should be refelct in other obj in 1 of field. how to write trigger for that

<------ Apex class--->>>>>

public class UpdateFields {
    public static void updateCustom1fields(List<Custom2__c> listOfCustom2){
        try{
        if(listOfCustom2 != NULL){
            System.debug('subhasis');
            List<Custom1__c> existingList = new List<Custom1__c>();
            existingList = [SELECT Id, Id__c, CTC__c FROM Custom1__c LIMIT 50000];
            Map<Id, List<Custom1__c>> idVsCustom1 = new Map<Id, List<Custom1__c>>();
            if(existingList.size() > 0){
                System.debug('subhasis');
                for(Custom1__c object1 : existingList){
                    for(Custom2__c object2 : listOfCustom2){
                        if(object1.Id__c == object2.Id__c){
                            object1.CTC__c = object2.Bonous__c + object2.Expense__c;
                        }
                    }
                }
                Update existingList;
            }
            
        }
        }catch(Exception exp){
            System.debug('Exception Cause'+exp.getCause()+'Line Number'+exp.getLineNumber());
        }
    }
}

trigger UpdateFields on Custom2__c (after Update, after insert) {
    
    if(Trigger.isAfter )
        if(Trigger.isInsert || Trigger.isUpdate){
        UpdateFields.updateCustom1fields(Trigger.new);
    }
}