Indians are so ubiquitous that everyone on the planet has had some negative interaction with them in the 21st century by now, whether that's through scams, shitty coworkers, smells, littering, internet presence, etc. The constant exposure to all of these things due to there being so many Indians exhibiting them has built up into this global backlash. It is genuinely a gestalt of anecdotes warping into a collective response.