1) While I grant Fisher was a better coach in other areas, on offense he is historically bad. The most predictable offense and a completely unprepared unit with little in the arsenal of how to create offensive opportunity
2) Greg Robinson - Simply a guy that couldn't be trusted and an already vanilla limited offense got dummied down even more. Plus, the number of times a back or tight end had to be used for help was nuts.
3) Not enough WR fire power. While the WR's were underachieving because of #1 and #2 as was every player on offense (Never seen so many players playing below there talent level), this unit needed more pop.
So it was 3 big things (But you could break these things down to more specific sub bullets.)
For example a sub bullet for bad offensive coaching would be:
Not playing Gurley on 3rd downs.
This is an example, but I could list them until the cows come home