A brilliant automotive engineer, Alec Issigonis made important contributions to the field of automobile design. The development of the recognizable Mini, which became an instant classic and has remained in demand for decades, is without a doubt his most noteworthy accomplishment. His humility and pride in the extent to which his work impacted others are reflected in the quote you cited.
Issigonis created the Mini at a time when fuel shortages and urban congestion made space efficiency essential. He created a compact yet roomy car that could comfortably fit four people and still be easy to park by ingeniously positioning the engine to sit sideways. Numerous manufacturers have imitated and modified this inventive design because it won over many hearts.
Consider Issigonis as an architect who created a home with distinctive features that made the most of the available space in constrained spaces. His inventiveness was admired by other architects, who started constructing homes based on his original design. The architect would feel proud that his ideas were not only acknowledged but also developed when people express gratitude for how others have drawn inspiration from him.
According to Issigonis's quotation, he was not preoccupied with the idea of being an innovator in a vacuum; instead, he was happy to see his work inspire others. In his view, progress is fueled by people exchanging and expanding on one another's ideas, much like trees shelter a variety of birds by allowing them to build their nests inside their branches.