“Behold therefore I have stretched out my hand over you, and have diminished your allotted portion, and delivered you into the will of those who hate you, the daughters of the Philistines, who are ashamed of your lewd ways.”
Compare here 2 Chronicles 28:18; Isaiah 9:12 which demonstrate that the Philistines were an ever present menace, taking advantage, when they dared, of any weakness. They occupied many towns of Judah ‘and dwelt there'. The extent of Israel's land was becoming less and less. Thus when Jerusalem rebelled against Babylon it would again give them their opportunity which they took (Ezekiel 25:15), for which they would eventually be punished by God (Ezekiel 25:15-17; Jeremiah 25:20; Jeremiah 47:1; Zephaniah 2:4-5; Zechariah 9:6).
So as a result of Philistine activity their ‘allotted portion' had been further reduced, and life became a burden. We have an example of this from the Taylor Prism where Sennacherib says of Hezekiah ‘His towns which I had despoiled I cut off from his land, giving them to Mitinti, king of Ashdod, Padi, king of Ekron, and Sillibel, king of Gaza, and so reduced his land.' All these were Philistine kings. But God here points out that the Philistines were more righteous than Jerusalem for they despised the flagrant behaviour of Jerusalem in welcoming many gods. Even the ungodly Philistines were mainly faithful to their own gods.