Worked in the industry for a while and there are countless reasons this could happen.

Waiting for permits, even with expedited permitting it can take months to hear back, then if even a single thing isn't up to code you have to start the process again, but there are tons of reasons why this can be a massive headache, especially for smaller individually owned restaurants.

Meeting city regulations, (seriously a spot near me wasn't allowed to open because the sign for their restaurant was more than two colors and had to wait over a month to hear back from the city), the regulations are also ever changing, one month you might have everything sorted, the next month you could be temporarily closed until X issue is dealt with and, even once you deal with it, have to wait to reopen.

Having the proper suppliers or hardware for your restaurant, some suppliers are notoriously annoying to work with. Having the right hardware can also be a massive headache. A smoker with a certain cover in one county/city might be completely fine, but drive 10 miles into the next county and suddenly you're outside city regs.

And that just scratches the surface, there are a ton of other bureaucratic hoops to jump through. There's a reason 50% - 80% of restaurants shutter within 5 years. Even restaurants with tons of patrons, constantly full, popular with locals, can fall victim to changes in code/regulations and fees/wait times that come with them.

Brutal industry.