He pled guilty. He chose poorly.
I probably would have done the same in that situation. Eight months plea bargain vs 20 years. Now if it went to trial, any reasonable jury would have acquitted but I would not gamble what would effectively be the rest of my life in prison on a stacked anti-Trump DC jury, that's for sure. He's already served six months so he'll be out in eight weeks. I can't blame him for that decision.
It's a travesty though. Those people were allowed to walk right into the Capitol and I have yet to see any violence or vandalism from those who were allowed in there to wave some flags and take some selfies. They looked like tourists!