What did Solomon do to the kingdom because of his sins?

Answer 1

1) Because of King Solomon's errors, God decreed that, later, Solomon's country (Israel) would be split into two, leaving Solomon's descendants with the minority of the Israelite Tribes, while the majority would be under Yerav'am (1 Kings ch.11).2) Trouble was caused for Solomon by Haddad the Edomite and Rezon ben Elyada (1 Kings, ibid).

It should be noted that "Solomon's sins" is putting it too bluntly. Jewish tradition states that King Solomon made a couple of mistakes but was otherwise eminently righteous.

A) Following the system of prophecy, which was to spotlight and severely castigate any errors in God's eyes, Solomon is blamed as if he personally worshiped foreign gods (1 Kings, ibid), although it was actually only some of his foreign-born wives who did so (Talmud, Shabbat 56b). Solomon's error was in not supervising their households more carefully.

B) The Torah prohibits Israelite kings from being very ostentatious (Deuteronomy ch.17). Solomon did permit himself to do so, which was wrong, but his motivation was the desire to be seen as lavish by foreign monarchs (1 Kings 10:23) in order to attract them to the service of God. In this he had success (1 Kings 10:1 and 10:24), but he died too young to bring about the fruition of his grand idea (he died at the age of 52).

See also:

The accomplishments of King Solomon

Jewish history timeline