Excel power query - Tranform JSON data correctly

in this way (almost) all done by GUI

let
    Source = Table.FromRows(Json.Document(Binary.Decompress(Binary.FromText("i45WMlTSUUpUitWJVjICspLALGMgKxnMMgGyUsAsQySFSCqRlELVxgIA", BinaryEncoding.Base64), Compression.Deflate)), let _t = ((type nullable text) meta [Serialized.Text = true]) in type table [value = _t, name = _t]),
    #"Changed Type" = Table.TransformColumnTypes(Source,{{"value", Int64.Type}, {"name", type text}}),
    grp = Table.Group(#"Changed Type", {"name"}, {{"grp", each _[value]}}),
    #"Extracted Values" = Table.TransformColumns(grp, {"grp", each Text.Combine(List.Transform(_, Text.From), ","), type text}),
    #"Split Column by Delimiter" = Table.SplitColumn(#"Extracted Values", "grp", Splitter.SplitTextByDelimiter(",", QuoteStyle.Csv), {"grp.1", "grp.2"}),
    #"Changed Type1" = Table.TransformColumnTypes(#"Split Column by Delimiter",{{"grp.1", Int64.Type}, {"grp.2", Int64.Type}}),
    #"Transposed Table" = Table.Transpose(#"Changed Type1"),
    #"Promoted Headers" = Table.PromoteHeaders(#"Transposed Table", [PromoteAllScalars=true]),
    #"Changed Type2" = Table.TransformColumnTypes(#"Promoted Headers",{{"a", Int64.Type}, {"b", Int64.Type}, {"c", Int64.Type}, {"d", Int64.Type}})
in
    #"Changed Type2"