Why were romanesque churches designed in such a specific way?

I believe it's a response to the period when they were created - that particular period asked for sturdy buildings inspired by ancient Roman architecture which this style obviously tries to mimic. Romanesque churches combine Roman and Byzantinian architecture in order to create buildings with thick walls, rounded arches, large towers, sturdy pillars, etc. I've attached an example of a Romanesque church - Basilica of Sant'Ambrogio in Milan, Italy.