John Gill Commentary 1 Kings 11:6

"And Solomon did that which was evil in the sight of Jehovah, and went not fully after Jehovah, as did David his father." — 1 Kings 11:6 (ASV)

And Solomon did evil in the sight of the Lord
As idolatry is, nothing more provoking to him:

and went not fully after the Lord, as did David his father ;
for though he did not relinquish the worship of the true God, and the service of the temple, yet inasmuch as he worshipped other gods besides, or connived at the worship of them, he did not wholly, and constantly, and solely serve the Lord, as his father did.