I'm a little surprised that it took this long for someone to get bent there with some of the dives I've seen (and done) there. The profile of the wreck is conducive to getting bent on aggressive dives if one isn't careful.
The reason for this is that the bottom is at about 130', while the top of the wreck is less than 50'. If one does a fairly long dive on the deeper portions of the wreck then follows it up with a leisurely tour, say back around the stern to the wheels then up and over the hull, one can go above the depth of the deeper required stops.
On one dive I did there we did this and when I looked at my computer (VR3) on beginning my ascent it was already claiming "missed deco". It got bent, luckily I didn't. One must keep in mind that their first stops may need to be conducted while still on the wreck.
As for gas, I believe I read that the lady that got bent was on EANx 32, probably the optimum gas for this dive unless one plans on hanging around the bottom. Their profile was apparently not overly aggressive but may have involved "sawtooth" type depths. Also, as Wendy said, there was likely another factor such as fatigue, dehydration, etc.
The Speigel Grove is one of the greatest wrecks going but it requires care if one wants to go at it aggressively.
Tom