Indentured servants from India and Bangladesh, living in GB, invented it to appease their captors. If one can find a traditional British Indian restaurant they'll find the Tikka masala bland as fuck: It's all cream and salt. They'll barely even use ghee or chili.
It's ironic how strongly some old world cuisines cling to spicy food these days, considering Europeans introduced Asians and Africans to chili in the first place, bringing them all the way from the americas not so long ago. Suddenly, only when it feels like lava on your tongue can it be called authentic even though they lived thousands of years without chili on an otherwise very similar diet.
The American chilis were a replacement for a local one, with the benefit that because there was more spice density could be stretched longer. Spicy wasn't invented by American peppers.
Often times, a new spice is simply surplanting a local not because the flavor wasnt there but because it was economically superior (you can stretch the same spice further)