Withdrawn after only 10 years of service, why?

It is a classic lifespan of a trolleybus ... without some major works done. And they obtained new articulated trolleybuses.

10 years is the typical lifespan of buses, trolleybuses have longer service lives. Even countries like Switzerland operate some of their trolleybuses for 30 years or longer.

Well yeah, however as these were made from bus chassis, sometimes not well adapted, there were often problems with axles etc., we have similar ones in Brno (articulated) and now after 12-14 years of service they are to be withdrawn, multiple often out of service due to mechanical failures. Furthermore, on low-floor chassis, major reconstruction works giving the vehicle a second or third life are technically imposible / financially very ineffective.

These were withdrawn due to the arrival of the new Trollinos. I say "due of" them because the city has committed to expanding the trolleybus network to electrify some bus lines. This didn't happen and they were faced with a surplus of trolleybuses. After public pressure, a few trolleybuses reappeared in service this year.

But why did the city abandon plans to expand the trolleybus network?

The right answer would be because of laziness.

Bus line 8 is now being converted into a trolleybus one. They only had to put in a few electric switches, modify some road markings and set up a station, in the rest trolleybuses will use the network of line 5. They started working in November 2022 and neither until today the trolleybuses don't run.