https://www.youtube.com/watch?v=gSxqZC6mApwI happened to stumble on a vlog about the Orient Express, and i can kinda see why the Lego set changed so drastically. the (current) Orient Express isn't about the locomotives anymore, and is more about the cars themselves. If i was Lego, i'd probably just remove the whole engine and give the set three cars instead; one for sleeping quarters, one for the Club Car, and one for the Diner Car. the Ideas submission was depicting the train as it was decades ago, but the license holders want it to be based on the current iteration, hence the change.
tl;dr blame executive meddling why the Orient Express set is shit.