Sounds simple. Many moons ago I seem to remember that a few of our bus runs were timed for a five minute train connection wait. From memory, traffic and passenger delays meant we rarely arrived on time. Usually arrived well after our departure time, regardless of whether the train had come (or gone).
So we would arrive late (frequently very late), pick up whoever was there, and go.
If you are going to task a bus to wait for a train, it would have to be a dedicated driver and vehicle, and would wait until the train arrived, regardless of the bus schedule that was to follow that timetable.
Too many variables unfortunately.
I agree that many part sound a lot simpler than they are.
With an hourly service on one of the legs, and perhaps a more frequent service on the connecting leg, it becomes less of a problem. With the train gaps being two and a half hours in one direction, and two and a quarter in the other direction, and with a fixed appointment (of "interview" importance) at the end, it was / is not clever.
As service reliability improves (remember, that's big thing that the magic wand of nationalisation is set to bring), the connection problem is not entirely eliminated but it should be a degree or two less.
Certainly network co-ordination should help. After my appointment and my walk via Coate Water to Old Town, I picked up the bus from there to Devizes which runs every hour on a Sunday and I got home even before the next train would have left Swindon. I couldn't help but notice that 2 buses an hour were leaving the stop in Swindon for or via Wroughton at 4 and 59 minutes after the hour. Sound OK - until you note that the gap between them is 5 minutes or 55 (I grant they take different routes), that the real time display was out of action, and the times for the Devizes bus were on a poster in which the minutes after the hour were hidden by the frame!