Index Optimize cause DB size increasement
Yes that is normal.

See: Disk Space Requirements for Index DDL Operations


  When a new index structure is created, disk space for both the old
  (source) and new (target) structures is required in their appropriate
  files and filegroups. The old structure is not deallocated until the
  index creation transaction commits.
  
  The following index DDL operations create new index structures and
  require additional disk space:
  
  
  ALTER INDEX REBUILD
  


So if one of your indexes was rebuilt by the script, the size needed for that operation was the size of the old index structure + the size of the new index structure for the time the operation was running.

Once the new structure is in place the old structure is removed and free space remains inside the data file, but it is not returned to the operating system so your data file ends up larger but should include some free space that will be reused in the future.

Also take a look at Index Disk Space Example


  Total disk space required to support both the source and target
  structures for the duration of the index operation is 816 MB (363 +
  453). The space currently allocated to the source structures will be
  deallocated after the index operation is committed.