Now how Ruth & 1 Samuel fit together.
There are numerous connections, esp. between the last ch. of Ruth & 1 Sam 1.
E.g. unique phrases:
Ruth 4:15 "she is more to you than seven sons"
1 Sam 1:8 "Am I not more to you than ten sons?"
Naomi self-describes as Mara 'bitter' (Ruth 1:20)
Hannah is described, by the same root, as 'bitter of soul' marath naphesh (1 Sam 1:10)
Both have 'give seed' in a wish (Ruth 4:12; 1 Sam 1:11)
'may a full reward be given you by the LORD, the God of Israel' (Ruth 2:12)
'may the God of Israel grant your request' (1 Sam 1:17)
Adjacent chapters both have 'and she bore a son' (וַתֵּלֶד בֵּן, Ruth 4:13; 1 Sam 1:20) & naming
'I have found favor in your eyes, my lord, for you have comforted me and spoken kindly to your maidservant' (Ruth 2:13; cf. 2:2, 10)
'May your maidservant find favour in your eyes' (1 Sam 1:18)
Connections (e.g. 'better than N sons') are sufficiently striking that the order of books & composition of books cannot be separated.
This doesn't mean Ruth doesn't also fit superbly after Prov 31:
Humans wrote the books of the Bible, which just have uncanny ways of fitting together.
I wonder how we could explain that...