It seems like it should be-
SELECT * FROM users u JOIN last_user_event_1 e USING (user_id,user_group);
--OR--
SELECT * FROM last_user_event_2 e;
for them to produce the same result set, since the last_user_event_2
already (could) have users info in it very simply by select * instead of
e.* in that view definition.
Are there other important joins/where/order by/limits that would be on this
"main query" that is just SELECT * FROM ____ right now which you have
dropped to try to simplify the example?