Final answer:
ExxonMobil maintained a focus on existing energy sources rather than investing in new types of energy because of the substantial energy investment needed for transition and the practical and economic challenges involved.
Step-by-step explanation:
According to the interview with ExxonMobil, they did not continue to invest in newer types of energy due to a focus on existing energy sources. This emphasis can be understood within the context where transitioning to renewable energy infrastructure requires substantial energy investment at a time when energy is already in limited supply. Furthermore, there are significant practical and economic challenges to developing a comprehensive energy portfolio from alternatives that permit a continuation of current lifestyles. Private markets may also offer insufficient incentives for the development of new technology due to economic and logistical barriers.