Hello Marcel
All routes learned via EIGRP are contained within the topology table, whether they are actively being used (in the routing table) or not. These routes are examined by EIGRP and only the route with the best metric is placed within the routing table. The rest of the routes still exist in the topology table however.
So, the routing table will only have a single route to a particular destination by default (unless two routes have an equal metric of course). In order to determine if a route can be used for unequal load balancing, the variance value is used and the calculation as described above is implemented on the metrics found in all routes within the topology table. If the metric of the route fulfills the metric * variance > FD condition, then it is then installed in the routing table as well, as a secondary, unequally load balanced route.
So the topology table is used in this whole evaluation of routes because it is there that all the available routes and their metrics are found.
I hope this has been helpful!
Laz