5:12 And through the hands of the apostles many signs and wonders were done among the people. And they were all with one accord in Solomon’s Porch. 13 Yet none of the rest dared join them, but the people esteemed them highly. 14 And believers were increasingly added to the Lord, multitudes of both men and women, 15 so that they brought the sick out into the streets and laid them on beds and couches, that at least the shadow of Peter passing by might fall on some of them. 16 Also a multitude gathered from the surrounding cities to Jerusalem, bringing sick people and those who were tormented by unclean spirits, and they were all healed.
Miracles. What is the point of them? Why does God intervene in miraculous ways in some cases and seem silent in others? Why when the Pharisees kept asking Jesus to perform a miracle as a sign of His authenticity did He refuse saying "A perverse and corrupt generation seeks for a sign."
The fact is He barely performed any miracles in Jerusalem but now the disciples are seeing miracles performed through them left, right, and center in the heart of the city. Why the change?
It's for the same reason He exposed Ananias and Sapphira. The whole religious world was in tumult and confusion. On one side the religious and political leaders were trying to discredit Jesus and His followers and maintain the status quo. On the other hand a band of former fishermen and misfits were taking Jerusalem by storm. Buildings were shaking. The lame were leaping and sick people were being healed just by being in the shadow of the apostles as they passed by. God was making it impossible to not realize where He was at work.
When Jesus died the huge curtain in the temple dividing the Holy Place from the Most Holy Place was torn in two from top to bottom. It was a Divine act and clearly signaled a change. Now the very fabric of the Jewish nation was being torn in the same way, leaving only two distinct sides. Either you were with Jesus or against Him. It wasn't a war of guns or swords. It was a war of belief.
Jesus was making it as hard as He could make it for anyone to reject Him. He wanted everyone to understand that He was the One and He wanted to save them all despite the fact they had killed Him.
Miracles are tricky. They are never the source of our faith. If they were then everyone who ever saw one would believe. Miracles are only an evidence. Belief is a choice based on evidence. What we need to understand is that God has reasons for everything He does and does not do. We must trust that no miracle is as key to saving people as a great miracle is because everything He does is calculated to save as many as possible.