Then the Jews demanded of him, “What miraculous sign can you show us to prove your authority to do all this?”
Notice that the Jews do not dispute the rightness of Jesus’ actions, but they do demand a sign to prove His Messianic claim which they fully understood.
Jesus had already given them 2 signs: the action itself and the fact that there was no opposition to His deeds even though He acted alone.
Speaking of which, where were the Temple guards? Why didn’t the vendors defend themselves or their merchandise? Jesus was vastly outnumbered and yet nobody opposed Him. Nobody stands before the wrath of God (Psa 114:5-7). We often think of Jesus as being meek and mild but we need to have our knowledge of Him stretched until we realize that He gets angry when His Father is maligned or His people are kept from coming into a relationship with Him.
Psalms 114:5-7 Why was it, O sea, that you fled, O Jordan, that you turned back, you mountains, that you skipped like rams, you hills, like lambs? Tremble, O earth, at the presence of the Lord, at the presence of the God of Jacob,