With too many Kings. Too many Popes. Paradigms force us to make decisions, early and often. Data are not being gathered selectively, but indiscriminately, atheoretically. Nearly every reasonable study from the past 30 years is being re-run nowadays, with an fMRI machine attached to the project.
Competition is at the root of creativity.
They were opposing theories, contrary to the exclusion of the other. Whenever and wherever possible, data was collected and technology was developed in order to refute the other model. Sometimes it's not clear what data is relevant in the real world, what observations should be made. But with competition one's eyes are often widely opened, one's priorities become crystal clear. So was the case with the young field of cosmology.