[Act 15:24 KJV] 24 Forasmuch as we have heard, that certain which went out from us have troubled you with words, subverting your souls, saying, [Ye must] be circumcised, and keep the law: to whom we gave no [such] commandment:
It doesnt say they were imposters
They gave no commandment to the Gentile believers to be circumcised and keep the law
Acts 15:1-5 KJV
1)
And certain men which came down from Judaea taught the brethren, and said, Except ye be circumcised after the manner of Moses, ye cannot be saved.
2) When therefore Paul and Barnabas had no small dissension and disputation with them, they determined that Paul and Barnabas, and certain other of them, should go up to Jerusalem unto the apostles and elders about this question.
3) And being brought on their way by the church, they passed through Phenice and Samaria, declaring the conversion of the Gentiles: and they caused great joy unto all the brethren.
4) And when they were come to Jerusalem, they were received of the church, and of the apostles and elders, and they declared all things that God had done with them.
5) But there rose up
certain of the sect of the Pharisees which believed, saying, That it was needful to circumcise them, and to command them to keep the law of Moses.
In the first verse, we're not told whether these were believers or not. But in the 5th verse, this is believing Pharisees. I don't see any indication that these were "imposters".
Furthermore,
Acts 21:20-21 KJV
20) And when they heard it, they glorified the Lord, and said unto him, Thou seest, brother,
how many thousands of Jews there are which believe; and they are all zealous of the law:
21) And they are informed of thee, that thou teachest all the Jews which are among the Gentiles to forsake Moses, saying that they ought not to circumcise their children, neither to walk after the customs.
Which I believe relates to,
Jeremiah 31:31-33 KJV
31) Behold, the days come, saith the LORD, that I will make a new covenant with the house of Israel, and with the house of Judah:
32) Not according to the covenant that I made with their fathers in the day that I took them by the hand to bring them out of the land of Egypt; which my covenant they brake, although I was an husband unto them, saith the LORD:
33) But this shall be the covenant that I will make with the house of Israel; After those days, saith the LORD,
I will put my law in their inward parts, and write it in their hearts; and will be their God, and they shall be my people.
and
Ezekiel 11:17-20 KJV
17) Therefore say, Thus saith the Lord GOD; I will even gather you from the people, and assemble you out of the countries where ye have been scattered, and I will give you the land of Israel.
18) And they shall come thither, and they shall take away all the detestable things thereof and all the abominations thereof from thence.
19) And I will give them one heart, and I will put a new spirit within you; and I will take the stony heart out of their flesh, and will give them an heart of flesh:
20)
That they may walk in my statutes, and keep mine ordinances, and do them: and they shall be my people, and I will be their God.
I think this will be fulfilled completely in the Kingdom Age. Meanwhile,
I think the regenerated Israelites would have found impediments to keeping the Law gone, and in their longstanding desire to keep the Law, they find they can, and become zealous to do so.
Much love!