I was kind of in the same situation...my parents had a lot of money saved up for my college and were planning on having a lot more invested by the time I was 18..However, when i was 12/13 my dad lost his job and so they needed all my college money to pay for bills.
As for your situation, yeah I would super uber pissed. The person who said something about being over 18 and paying for your own stuff...yeah no. if they had that much money saved up for your college they had obviously been saving long before you turned 18...therefore if it was set to be your college money, you have a total right to be angry. I would probably be like "well i hope that business it going to bring in even more money"..because if not then what a waste!
I wouldn't stay angry with them forever, definitely don't let it ruin your relationship with them...But talk to them about it...maybe they had the impression that you didn't want their help with college at all?? Idk..
good luck withe everything!