Newton lived in about17th century. He preceded Einstein by more than 200 years. At that time, he didn't have a complete mathematical system and calculus, so he couldn't study the state changes of similar limits in detail. So Newton invented calculus in order to study his own mechanical state, so because he invented calculus, Newton is also called one of the three outstanding figures in mathematics, because calculus accounts for a considerable proportion in higher mathematics. The example you will learn when you study calculus in higher mathematics is to do mechanical experiments.
Einstein lived about 1900 years old, and when he died, he was 1955 years old. At that time, the basic system of mathematics had been established, and he did not need to explore the mathematical system to carry out his own research. His biased research is also more astronomical research. He also has his own insistence on physics about the knowledge of general relativity and special relativity of the universe. For example, he won the Nobel Prize for the conclusion of the duality of light and glass, because the theory of relativity was great, but not many people could really understand it at that time. Einstein won the Nobel Prize for his conclusion on the duality of light.
Generally speaking, they live in different times, and the direction of studying physics is naturally different. Newton was a great physicist, but he didn't think he could be a great mathematician at first, but when he studied mechanical gravity, he found that he couldn't just express some phenomena, so he took calculus. Most of what Einstein did was theoretical research. Although there was calculation, it was not the main thing, and there was a relatively complete mathematical system at that time, which was enough to meet his research needs.