What is one reason why the abundance of angiosperms could have helped small mammals be successful and produce more offspring?

The reason why the abundance of the mammals be successful is that it provides food and oxygen for the survival of the mammals.

These plants also attract the mammals which helps in mating of the animals and producing more offspring.

A healthy animal will only lead to the producing more healthy offspring and by getting proper food the animals will produce successful offspring.

substitution is the answer in this case