The best ideas arise from a passionate interest in commonplace things

To be successful in any areas of life or any work one is entitled, one must have develop adequate interest in that field. the issue presented in the passage is agreeable to an extent that an interest is essential to be able to get sufficiently engrossed in a work or field.
However a claim that the best ideas arise from a passionate interest in commonplace things is too narrowed down.

Before presenting the point to complement it, it must be noted that the term commonplace things is too critical to be drawn as a conclusion. For example to be able to get the best ideas in any field of science, it is not essential to have a passionate interest in commonplace things. However it is imperative that a person must show adequate interest in the particular field of study.

Firstly, having a passionate interest in the field will provide the required motivation to pursue the field. For example a interest in physical fitness would automatically motivate a person to do it regularly.In the other way round, if a person does not have adequate interest, he would feel lazy to do it. It would need another person or friend to motivate him regularly and go to the Gym. So having an interest in the filed provides adequate motivation to regularly do it and only constant and regular performance can help a person develop good ideas.

Secondly, having an interest would make a person spend a lot amount of time and energy for that field. If you ask any person why he did not come for particular thing, he always has an excuse that the did not get time. But it is commonly observed that if a person has an interest, he would make time and dedicate time for that filed. Usually, The amount of time one spends in an field is directly proportional to the ideas that a person develops. This also helps him to spend more energy in the field of interest which is sure to give thought provoking ideas.

For a person who loves music, he loves to spend a lot of time with practicing and playing it. I know of a friend of mine who is now a well Known keyboardist, who also was in same music class of mine, he would spend 8-10 hours just practicing any musical notes. On the other hand, it would be very difficult for me to spend 2 hours with it. It was because I liked music but I did not have a passionate interest as him.This gave him a great edge over other and he used to develop great ideas and musical pieces which even the Music teacher found amazing.

So to conclude, it must be noted that a passionate interest in a field surely help develop great ideas. But there might be some exceptions for the vest ideas which can be an accidental one. This is however a very small possibility because even an accidental idea can help develop a interest later on in the life.