The plan was for AJ McCarron to be the starter, not Peterman. Peterman was much better in camp and in preseason than McCarron and he won the job. The plan was always for Allen to sit until ready.
Getting Fitz was not an option that I remember even being there.
If you must find blame, and you obviously do, then blame Beane for not bringing in a better veteran QB. Then you can also criticize Andy Reid for keeping Mahommes on the bench a full year. By your logic the Chiefs would have 2 Super Bowls by now, not one.