What motivates a person to invest in a particular sector of the economy?

Profit

The skills one have and passion for what he wants to do

Return on investment

The investment where you align your passion and the market need, you can start investment slowly but must first carryout research for example if you have passion for health food then your market should be in gyms or rich woman who want to maintain body but at the same it will it be profitable if there are three ticks you can go ahead if not you need to research on ares you are not sure of

If your use of the word "Investment" is limited to money, I agree with those who maintain that a profitable return on the investment in money is the motivation.

As Comr Matthew states in his reply, there are other motivations. For the most part those motivations can be categorized as "Values" in terms of fulfillment, growing an enterprise supporting the community, solving an issue or helping others.

Knowledge of the role values play in business can directly impact success and become part of a marketing plan. For details please see the article linked below at the FREE web site I maintain for small business entrepreneurs as an extension of my volunteer work:

https://www.smalltofeds.com/2012/11/value-based-marketing-techniques-for.html

The first thing that motivates you is your PASSION. This is one of the great secret of every successful business that exist today. Have you think about falling back on your business? When you remembered how you like your business and what you are doing, the resources you have invested, time you have put on it, all these exist as a result of passion you have at first, this will make you to stick firm. Instead of quitting, passion allows you to take a little break, examine the areas you need to be improve and figure out the right and effective measure that will aid you to improve those areas and still moving forward till you get to the level of reaching your desired goals.

Secondly is humanity, you think of people you need to help, in your society, Organisation, People's that are in need, your relatives, your loved ones, you will observed that you have some certain roles to play in their lives, this will help you to keep pushing and never give up because..you want to be that problem solver that exist in your network where people will find and get value from. Hope this helps.. Thanks.

People invest for one of two reasons. They want to make either of these: (1) they want to make an impact, typically because it's something they're passionate about. Angel investors, friends and family are good for this category. (2)They want to make profits. Venture capital firms are good for this category.