That's why Indore is called as Mini Mumbai!
Most answers here rely on some characteristics of Indore that are found much more prominently in many other cities. Cotton mills, cosmopolitan culture, food habits and so on are not typical of either Mumbai or Indore. That way, even many more cities like Ahmedabad and Kanpur should also be called Mini Mumbai (or Mumbai should be called Big Indore / Ahmedabad etc.). This is where history becomes important.
During 1970s and 1980s, Mumbai was progressively falling under the grip of trade unionism and goondaism. These were the years of Mumbai Mafia (from Varadrajan Mudaliar to Naik Gang, all reached their peak years between 1960s to end of 1980s). The political support to these mafia (criminal as well as trade union one) made Mumbai businesses even more vulnerable. When businesses wanted to shift away from Mumbai, the options were either within Maharashtra, Gujarat, MP, or Karnataka. Within Maharashtra had the same political problems. Gujarat had it’s own stronghold of business networks. Karnataka had huge language barriers.
At such a time, Indore was a ready choice – no language barriers, basic infrastructure and connectivity present, law and order in good shape, and cultural similarities, as marathis were in commanding positions due to Holkar legacy. This is why, Indore started becoming a hub of business deals and settlements as well as a destination for many investments. The name “Mini Mumbai” for Indore originated in mid-1970s only.
However, Maharashtra recovered sooner than losing all the business to elsewhere and MP began falling, thanks to vulturous Congress politicians like Shyama Charan Shukla (brother of Vidya Charan Shukla, the villain of emergency years), Arjun Singh, Digvijay Singh, and their ilk. Therefore, when someone calls Indore as “Mini Mumbai” today, they refer to an old legacy only.
In present day, if any city comes closest to Mumbai, that would be Ahmedabad – business hub, highly entrepreneurial, well-connected, safest law and order situation. However, it doesn’t have the huge distance and crowd problems like Mumbai (and no sea-line).
