"gradually becomes evident" is correct and commonly used in written English.
It can be used when something is not immediately obvious, but becomes clearer over time. Example: As she spent more time with him, the depth of his intelligence gradually became evident.
As the kitchen scene progresses, it gradually becomes evident to the audience that the workers are the same people who were once accomplices in Siegfried's murder, although none of them apparently know it.
It gradually becomes evident, though, that the interviewer is Hunt's wife, concerned since the birth of their child about the risks involved in such impulsive means of bringing home the bacon.
After Aníbal offers Celestina shelter for the night, it gradually becomes evident that she is from the land of magic realism: she doesn't think of time the way most people do, and time doesn't treat her the way it does others.
It gradually becomes evident that the film can be read as something going on in the mind of a man wholly preoccupied by the problems of making a work of art, someone who has on his mind Graham Greene's cruel precept that "There is a splinter of ice in the heart of a writer".
It gradually became evident that Valenti, despite his self-deprecating appraisal, was bringing Johnson more than loyalty.
It gradually became evident that some arise from irregularities in Earth's rotation rate, others from minor tidal effects on Earth and the Moon.
There is a general conception that AOM is a bacterial disease but with the availability of sensitive diagnostic methods, it has gradually become evident that viruses play an important role in the pathogenesis of AOM.
It gradually became evident that the problems seen in Paris also existed in the suburbs.
A low-level circulation gradually became evident on satellite imagery within the disturbance.
In 2003, Ersoz et al. [ 8] reported the use of EST plus endoscopic papillary large-balloon dilation (EPLBD), and the usefulness of this innovation in patients with difficult-to-remove stones has gradually become evident.
Based on the above mentioned observations it becomes evident that gradual dissection of the hierarchically orchestrated supramolecular assemblies that constitute dentin collagen fibrils gradually reveals structural features that may impose critical limitations to the action of polymeric dental materials.
