Table with Clustered Columnstore Index bigger than a Clustered Rowstore Index
Unfortunately, you destroyed all the evidence that could have lead to an answer when you got rid of the CCI. 

I'd suspect a lack of maintenance (rebuilds/reorgs) lead to uncompressed rowgroups, or lots of deleted rows leftover in them. 

One way to test this would be to create a second copy of the table with a CCI on it and see if it's still larger. A good way to get answers about what's going on in column store indexes generally is NikoNeugebauer's CISL GitHub repo.