Flatten sublists within a bigger list

Flatten can be used to reshape dimensions by making use of its second parameter.

Flatten[#, {2, 3}] &@Transpose@data// MatrixForm

Transpose places your columns in rows then Flatten flattens over dimension 2 (each cell in each row - these contain a sub-list) and then over dimension 3 (each value in each sub-list of each row). This gives the the three columns you are seeking.

Hope this helps.

If it isn't closed, it should get an answer. As far as I can tell the shortest way is

Join @@@ list // Transpose

or as @C.E. pointed out

Flatten /@ list // Transpose