Why is the formation of the Earth a controversial topic?
Primarily because the "evidence" is not always clear.
We must infer what might have happened in the past from the things we observe in the present. There are no tangible records of the actual events - only the outcomes.
Thus, there are many places in our reasoning and decisions about evidence where we can have different opinions or even errors. Issues of timelines get even more complex as the inferences for dating materials are subject to severe sample integrity issues as well as the basic assumptions and calculations.
For example, while the equation for the elapsed time for the decay of a radioactive species is quite precise (the basis for radiocarbon and related dating), the assumptions of original material amounts and the errors in sampling can cause huge differences from extremely small numerical changes.