People with power get nervous when there's a throng of people marching and not for them.
The people shouting "Hosanna!" were not the power players of the Empire. They were crying out to Jesus, whose reputation as the Messiah had preceded him, and it's likely that a good many of them were seeing Jesus as the warrior king who would come to Jerusalem, rally the troops, and get the Romans kicked out of the holy city.
If that's what they were hoping for, it was a false hope.
Ironically, the Empire saw Jesus for who he was. He was regarding the people who the Empire disregarded. He was talking up some kind of Reign of God that had nothing to do with the Emperor cult. He was saying that signs of this Reign were when the sick were healed, the naked clothed, the hungry fed.
How sad for Jesus to have people who didn't understand as his friends and those who understood as his enemies.
Look at these people crying out "Hosanna! Save us!" They are us, the believers, the followers of Jesus.
And when we find he isn't going to take up arms for us, isn't going to even save himself, we're going to step back, watch what happens, and shake our heads, disappointed in this alleged messiah. We may watch in horror, but we're going to watch, nonetheless. We won't even believe that we're the troops we had hoped Jesus would rally.
But the Empire, they saw the truth. They saw the subversion to the "natural order" that Jesus represented. Empire is almost always paranoid, and Empire has a way of making the paranoia justified.
You can't maintain power when the lowest of the low start learning they are children of God.
So the week begins.