Jesus destroyed the temple by sending the Romans. The end of the law was also taught by Jesus and his apostles, especially in the letters of Paul.
In Matthew 5:17, Jesus specifically said that he did not come to abolish the law, and in Romans 3:31, Paul confirmed that our faith does not abolish the law, but rather our faith upholds yet, yet you are seeking to abolishing it rather than uphold it through faith. In other words, you do not have faith in God to correctly divide between good and evil through His law.
The Bible often uses the same terms to describe aspects of the nature of God as it does to describe aspects of the nature of God's law, such as with it being holy, righteous, and good (Romans 7:12), or with justice, mercy, and faithfulness being weightier matters of the law (Matthew 23:23), and it could not be accurately described as such if it were not God's instructions for how to act in accordance with those aspects of God nature. God's nature is eternal, so any instructions that God has ever given for how to act in accordance with His nature are eternally valid, such as with God's righteousness and righteous laws being eternal (Psalms 119:142, 119:160, and the only way for laws for how to act in accordance with God's nature to be abolished is for God to also be abolished.
For example, God's law reveals that it in accordance with God's righteousness to help the poor, so if that were to be abolished such that it was no longer in accordance with God's righteousness to help the poor, then there would no longer exist a God who has that as an aspect of their nature. So the rejection of the Law of Moses is a the rejection of the existence of the God of Israel, whose nature is described by its, and the Son is in the exact nature of the God of Israel (Hebrews 1:3), which he expressed through living in sinless obedience to the Law of Moses, so it is also the rejection of the existence of the Son. In other words, God's word can't be abolished without also abolishing God's word made flesh.
So why does Acts call them "false witnesses"? The Expositor's Greek Testament explains it this way: “false,” inasmuch as they perverted the meaning of Stephen’s words, which were no blasphemy against Moses or against God, although no doubt he had taught the transitory nature of the Mosaic law
Regardless of the degree to which they perverted the meaning go Stephen's words or the degree that they made things up full cloth, he did not say that they said he did, and all positions that use the words of false witnesses to support them should be reconsidered. Stephen said nothing to teach that the Mosaic Law is transitory, so you are also falsely putting words in his mouth, especially because if he had said that, then he would have been speaking blasphemy against Moses and against God. All of God's righteous laws are eternal, so they do not have a transitory nature, and neither does the God of Israel.