Or you could just read the IMHE page where they tell you exactly why they updated the model.
COVID-19 Estimation Updates
The main reasons are
1. Italy and Spain looking like they are peaking which gives more accuracy to when they project the US will peak
2. Giving different weights to different social distancing measures (before they were all given equal weight)
3. Changing the way they calculate uncertainty for distant future projections
4. More data from states where their case numbers were really low
This is actually the 5th update to their model. They have documentation of the other updates at the bottom of the page. Modelling is something that constantly changes as more data comes in. And as we see the effects of different social distancing policies, it will also be reflected in the modelling.
For the hospital utilization data, the old model was based on the CDC report for hospital use back in mid March for the whole country. The new model is based on more up to date state specific data for hospital use.