Because you recreated lists in the subsite, the links of lists are changed, which caused the lookup column to be broken.
To resolve this issue, you need to recreate the lookup column or repair the lookup column by using PowerShell.
Add-PSSnapin Microsoft.SharePoint.PowerShell -ErrorAction SilentlyContinue
#Configuration Parameters
$SiteURL="subsiteurl"
$ListName="list2"
$LookupColumnName="lookupcolumn"
$LookUpListName="list1" #Parent List
#Get the Objects
$Web = Get-SPWeb $SiteURL
$List = $web.Lists[$ListName]
$LookupList = $web.Lists[$LookUpListName]
$Column = $List.Fields[$LookupColumnName]
#Update column schema
$Column.SchemaXml = $Column.SchemaXml.Replace($Column.LookupWebId.ToString(), $Web.ID.ToString())
$Column.SchemaXml = $Column.SchemaXml.Replace($Column.LookupList.ToString(), $LookupList.ID.ToString())
$Column.Update()
Write-host "Lookup column fixed!" -f Green
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