John Gill Commentary 1 Kings 11:9

"And Jehovah was angry with Solomon, because his heart was turned away from Jehovah, the God of Israel, who had appeared unto him twice," — 1 Kings 11:9 (ASV)

And the Lord was angry with Solomon, because his heart was
turned from the Lord God of Israel
Or from the fear of him, as the Targum, which must in a great measure be cast off, or he could not have given in to idolatry in any shape as he did; for it was for that the Lord was displeased, the which nothing is more provoking to him, as may be often observed:

which had appeared unto him twice ;
once at Gibeon, and again after his prayer at the dedication of the temple, (1 Kings 3:5) (9:2) , which is mentioned here as an aggravation of his sin, that he should fall into it, when the Lord had condescended to appear to him so graciously.