As a former small business owner (20+yrs photography studio) I will take a stab at this.
Low wages and bad bosses.
It’s that easy.
So many business just pay terrible wages, doesn’t really matter what the business makes or sells, wages rule who applies and who you get to pick from.
Add in managers/bosses who believe being an autocrat or an asshole is the way it has to be, and people leave, quickly.
I found when hiring assistants or cashiers performance bases pay was a great motivator. I set a reasonable goal for sales and when met, everyone gets a bonus. Top performer get another.
When employees get out of hand or argue with each other or a customer I step in immediately. I once quietly told two girls if they can’t work together both can leave now and don’t come back. Since it was the highest paying photo-assistant job in Las Vegas, everyone got back to work, false smiles and all.
When a customer is involved, I offer a full refund and ask them to leave. (Only had to call the cops once, trespassed her big ass and she just wanted to yell at me) I talk to the employee privately and get their side. Generally I always take my peoples side, until it become a pattern then let them go.
Unfortunately, fast food franchises are so far in debt generally a wage increase is hard to swallow. This is usually indicative of poor long term planning or mismanagement. Business fail because of bosses/owners/managers.
Your business fails because.
You opened up in a saturated market.
You hired the wrong people.
Your borrowed too much money and can’t afford the loan and wages.
Terrible location
Unforeseen event (pandemic/fire/embezzlement)
You are clueless about business.
That is a very large part of the problem.