Why is there a collation conflict between system views
sys.server_triggers is a server view, so it has the server collation. sys.triggers is a database view, so it has the database collation. You have a DB that has a collation different from the server. QED. Repro:

create database foo collate Latin1_General_CI_AI

use foo

select tr.name
from sys.triggers tr
union all
select tr.name
from sys.server_triggers tr;