1. It is important that you point out to students that Bach and Vivaldi represent the end of the era. They were also masters who inherited a long tradition of compositional practice. Dozens of other composers wrote considerable numbers of concerti grossi by (this being the preferred type early on) as well as hundreds of solo concertos.
2. You should point out that patronage was the system by which a composer could have a successful career. A composer could work in an aristocratic household, producing music for entertaining guests, or could work in a church. Bach held both types of positions. Vivaldi worked at an orphanage that was supported by wealthy aristocrats.