As one can read from NK, Torah was more or less observed up until the time of David.
David was the first to propose the idea of the stone Temple that was foreign to the Torah.
David's son, Solomon, managed to take the Ark from the Tabernacle and move it to the stone Temple (1st Temple) that he and his father had built.
How did this happen? On what authority?
Torah explicitly states that anyone foreign approaching the Tabernacle must be killed. The Ark and the Tabernacle were sanctified by Moses and were Holy so only Levites and Kohanim could serve in it. The Ark was also sanctified so no one was allowed even to enter into one room with it... So having said all this, how did Solomon managed to take the Ark? I do not know. NK does not state this very important detail.
Was there a revolt? Did Solomon kill the guarding Levites to take the Ark?
Or, perhaps, by the time this happened, Levites abandoned the Torah and were complicit to establish some new and foreign order of things...
Once again, NK is silent about this, so one can only speculate.
What is clear is that the dedication of the 1st Temple was the turning point for the Hebrew nation. By the time of the 1st Temple, Hebrews completely abandoned the Torah and started following this new order of things where the center of worship was not the light, portable Tabernacle, but rather impossibly heavy, stationary stone Temple.
Of'course, once the 1st Temple was destroyed, things got even worse. They built a second Temple, which was not even supposedly sanctioned by God (Herod's Temple) at which time we see the birth of Judaism which is a religion that has nothing to do with what Written Torah says. Also, completely foreign idea.
Now most Hebrews do not even know the Written Torah. No sure, they know they basic narrative but they have absolutely no understanding of a single word from it. This is what is known as Rabbinic Judaism, or Judaism in general...