Pope Francis has been in critical or serious medical condition for over 2 months - pneumonia - requiring non-invasive ventilation, high-flow oxygen, and blood transfusion - and early-stage kidney failure.
Holy Week (Palm Sunday through Easter Sunday) is busy with ceremonies in the Catholic Church, VERY stressful for a man in Francis' frail condition.
If "blame" is a word proper to this context, I'd "blame" Francis' 8 days of duties and his choice to do them. IOW, Francis did what he believed he should do, and the cumulative stress was too much for his frail system to sustain.
As for DU, haters gonna hate, facts be damned.