I think from the very start, there had been two distinct British views of Indian food- one experienced by the "Nabobs" who wanted to and could afford to maintain themselves (and consequently their kitchens) in the style of the Mughal aristocracy, and the views of the average British soldier or clerk.
The former was influenced by what was then North Indian high cuisine, which was both resource and time-intensive. These would have been complex dishes requiring multiple people laboring over the course of several hours or even days, perhaps slightly modified according to the tastes of the Patron. This never really migrated to the UK because of the aforementioned logistical problems, as well as an unwillingness on the part of the Nabobs to, well, appear as "Nabobs". People like Clive and Hastings, who were already under great suspicion and mistrust over their ill-found wealth, would hardly flaunt their extravagant lifestyle back home.
The latter view and the one I suspect really lasted is those of the more common British individuals who stayed in India or the Indians who emigrated to Britain. They basically took the version of Indian cuisine being cooked in the communal kitchens of the great market cities or the army camps. This was by necessity much watered-down food cooked for large numbers, by people who often couldn't afford to buy or didn't have access to spices by themselves. Hence "Curry powder" and a variety of rice-based dishes, which could be prepared relatively quickly.
I remember watching a video on something similar about Chinese-American cuisine, and why it seems like a parody of actual Chinese cuisine- basically it was Chinese food cooked by poor immigrants without authentic ingredients, who in any case didn't know how to cook very well.
Edit:Wrote "views of British food", instead of "British views of Indian food"