Jamieson, Fausset and Brown on 1 Samuel 7:2

2. the ark abode in Kirjath-jearim ... twenty years--It appears, in the subsequent history, that a much longer period elapsed before its final removal from Kirjath-jearim (2Sa 6:1-19; 1Ch 13:1-14). But that length of time had passed when the Israelites began to revive from their sad state of religious decline. The capture of the ark had produced a general indifference either as to its loss or its recovery.

all the house of Israel lamented after the Lord--They were then brought, doubtless by the influence of Samuel's exhortations, to renounce idolatry, and to return to the national worship of the true God.

1Sa 7:3-6. The Israelites, through Samuel's Influence, Solemnly Repent at Mizpeh.