I wish I knew! I think Lovie's defense lends itself to be more effective against more traditional offenses, especially now that we've been playing a 4-3 most of the time. The only real spread offense we've played recently was on a flooded field with a backup QB and multiple injuries... With that said, I don't think(?) we would perform as poorly if we replayed those teams. Or at least I'm pretty sure? I do think we have clearly improved over the year, and like BZuppke said, it's likely a combination of the 2 factors. Iowa beat us 63-0 last year and they run a more traditional offense, so clearly we have improved.
I think it's pretty plausible to expect some ongoing struggles against spread offenses going forward unless Lovie is willing to make some adjustments, but I think for the time being he's probably earned the benefit of the doubt until we face them again. Probably won't be until next year unless we face one in a bowl game.
A spread was not even remotely the issue. The issue was personnel.