Complex sentence: Theoretically, the honour of electing members of Parliament belonged to the wealthiest and most flourishing towns in the kingdom, thus, boroughs that ceased to be successful could be disenfranchised by the Crown.
Split into simpler sentences: Theoretically, the honour of electing members of Parliament belonged to the wealthiest and most flourishing towns in the kingdom. Boroughs that ceased to be successful could be disenfranchised by the Crown.