The problem isn't that we stray from following God's law. As Moses pointed out, we DON'T want to keep God's law. "Straying" from it is just simply an excuse.
I'm reminded of the incident in Jeremiah:
Jeremiah the prophet said to them, "I have heard you. Behold, I will pray to the LORD your God according to your request, and whatever the LORD answers you I will tell you. I will keep nothing back from you." Then they said to Jeremiah, "May the LORD be a true and faithful witness against us if we do not act according to all the word with which the LORD your God sends you to us. Jer 42:6 Whether it is good or bad, we will obey the voice of the LORD our God ...
At the end of ten days the word of the LORD came to Jeremiah. Then he summoned Johanan the son of Kareah and all the commanders of the forces who were with him, ... and said to them, "Thus says the LORD, the God of Israel, ... If you will remain in this land, then I will build you up and not pull you down; ...
When Jeremiah finished speaking to all the people all these words of the LORD their God, with which the LORD their God had sent him to them, Azariah the son of Hoshaiah and Johanan the son of Kareah and all the insolent men said to Jeremiah, "You are telling a lie. The LORD our God did not send you to say, 'Do not go to Egypt to live there,'
It isn't that the Jews have strayed from the Torah. They rebel against the word of God-just like everyone else. It is our sinful, rebellious nature that causes this. One cannot live by the law because our hearts are openly rebellious. And no matter how much one may think they are conforming to the Torah, they will never follow it completely.
A sacrifice has been paid to atone for this behavior through Christ His Messiah. But the Jews are still in open rebellion to God's solution just as they were with God's solution spoken through Jeremiah.
On the first Shavu`ot G-d spoke directly to perhaps some three million people. This had never happened before and has never happened since. Until it does, this is the supreme revelation that judges all others. The Prophets must be interpreted in light of the Torah. Any interpretation of the Prophets that is contrary to Torah is a false interpretation. Period. But of course, try explaining this to a chrstian.
In the portion of the Torah called Ki-Tavo' (Deuteronomy 26:1-29:8) there is a very long section of the terrible consequences of deviating from the Torah. It also predicts the long exile of the Jews for that very reason. There is not a word about exile being a result of "rejecting the messiah." This is a foreign meaning forced into the text. Out of all the 613 commandments of the Torah, there is no commandment to "accept the messiah," because when he comes it will be obvious to all. And there's no negative commandment against "killing G-d" for the simple reason that G-d can't be killed (but again, try telling that to a chrstian).
I am quite aware that none of this will make it into your head, but it is quite frustrating to see the dishonestly of chrstians who insist that the Jews are being punished for keeping the Torah (instead of abandoning it for chrstianity) when the Torah itself says the exact opposite.