Why is Moonsucks experiencing a decline in revenue?

I was preparing for my mock interviews and this was the case given to me by my friend who is also a product manager. She is very good with interviews and case studies, hence I was not expecting an easy RCA.

Case:
Moonsucks is the name of the restaurant located in Dubai (Central) near Burj Khalifa and the main tourist areas. Do an RCA of the same as there has been a decline in the revenue from the past month at Moonsucks.

Clarifying questions:

1. How much decline in the revenue
2. Can you specify the season, month, year
3. Has there been any change in the opening and the closing time of the restaurant
4. What kind of cuisine do we offer?

Then, I went on to deep dive into the problem statement in terms of the internal and external factors that might impact the revenue by using the PESTEL framework.

1. Have the UAE government made any changes in terms of tourist policies (some more political questions)
2. Are the neighbouring areas of the restaurants fine?
3. Have we faced any environmental issues/ natural calamities?
4. Any social issues of that country which has come up in the news such as an increase in unemployment, poverty, or anything along those lines?
5. Are we facing any technological issues such as supply chain, or big change which might impact the revenue?

After asking each question, they (the recruiters) will give hints as to what I should concentrate on next. So, if they say some laws have been passed by the government, then you ask questions like, have they impacted the tourists or the local people? Has there been any change in the overall footfall?

Now, let us discuss some possible internal factors which might have impacted the revenue:

1. Have we made any changes to the menu
2. Have we made any changes in terms of staff, chefs, or any other stakeholders?
3. Are we buying raw materials from the suppliers, any changes on that part?
4. Have we received any bad ratings?
5. Are tracking the right metrics?
6. Have we made changes in terms of new technology which new computers to issue bills/cheques which might have increased the waiting time of the customers?
7. Any new additions to the menu?
8. How many other hotels are there in the neighbouring?
9. Any new entry?
10. Can you tell me about the retention rate?

I got my answer in the competitor part because when I asked about the competitor she told me that there are two restaurants (1 Morrocon food, I vegan) and another vegan restaurant which has opened recently. Hence, I immediately thought that this could be one of the reasons because as people are becoming self-aware as to how the environment is getting impacted due to non-veg food, some of them have switched to vegan. As it was a new year, hence, people would have made resolutions to be vegan