Question: How could a really intelligent species be kept from developing? For clarification, this species is the only creature of intelligent thought on the planet and they have a population of about 50 million across the planet about the size of the moon. However, they can't develop to the level that Britain reached in the industrial revolution.

Answer: 
Give them the internet.

Give them e-mail, chat, and Zoom. Give them instagram, Facebook, TikTok.

Gmail.

Youtube.

Give them Twitter.

They will forget all about the stars.
They're too busy. The species has developed a hierarchy. Some individuals are at the top, and rule over everyone else.

Those at the top demand that those under them work. The work mostly doesn't advance society. Some of it maintains the status quo by keeping everyone fed who deserves to be fed, and the rest of it mostly just feeds the ego of those at the top.

Those at the bottom are promised that if they work long enough (tens of thousands of hours), they can become a ruler themselves and won't have to work any longer. They are told - gaslit - that working long hours will set them free and if they are not free it's their own fault for not working hard enough. But if they *don't* work, even though this society has abolished the death penalty, they will be denied access to basic necessities like food and shelter, and caused to die anyway.

As such, even the most intelligent members of the lower caste are too busy fulfilling their obligations to actually do anything with their intelligence.

Remind you of any other known intelligent species?