Step 1: Understanding the Concept:
During the colonial period, European powers often tried to remove significant archaeological artifacts from colonized lands to fill their own national museums.
Step 2: Detailed Explanation:
When the Sanchi Stupa was "re-discovered" in the $19^{th}$ century, its gateways (toranas) were found to be in excellent condition.
The French, in particular, were very keen to acquire the eastern gateway to display it in a museum in Paris.
The English also had similar designs for their museums in London.
They requested the then ruler of Bhopal, Shahjehan Begum, for permission to take the gateway.
Fortunately, the Begum and her successor Sultan Jehan Begum provided them with high-quality plaster casts of the gateway instead, which satisfied the Europeans and kept the original structure at Sanchi.
Step 3: Final Answer:
The interest was primarily to display the original eastern gateway in European museums.