Previous physics courses have presented many applications of Newton's second law ${\displaystyle F=ma}$ where the force, ${\displaystyle F}$, is given or is a combination of constraining forces and given ones. The downside was that each phenomenon has its own set of forces to remember and different constraints required different formulations.

To get to the principle of least action we shall start with ${\displaystyle F=ma}$ (as in Schaum, Goldstein and Kibble). We could have given the principle as an axiom (as in Landau and Lifshiftz) and found ${\displaystyle F=ma}$ as a consequence. Since you are already familiar with ${\displaystyle F=ma}$ the first path is probably more comfortable.