His IV blew out. Happens all the time to live folks in hospitals. You don't like it, but you don't normally consider botched medical care. You consider it bad luck, at least the first time. Or you say you have bad veins. IV drug users will tend to have bad veins. They probably deserve more than their statistical share of death sentences. Should they be immune because of their past bad habits? I doubt blowing their own veins ever stopped them from shooting up.
When the perp's IV blew out they stopped the execution rather than start another IV. Then God killed him anyway. Then the perp's suffering really started! It all went according to the big plan.
The perp also put up a battle royal to frustrate the execution and disrupt the whole procedure. That’s why they had to cut down to find his femoral vein. IOW he pooped into his own nest and has to live with it for eternity.