While the attack in Delhi wasn’t directed at India, it did happen on Indian soil in the national capital. It also injured several Indians who were passengers in a vehicle traveling next to the one that the bomb was planted on. That Iran would operate on Indian soil to commit attacks is distressing to the security community in Delhi, and no doubt has instigated multiple discreet discussions between Centre and the Iranian embassy.
That attack in Mumbai a couple of years ago was 1000 times more evil, more planned and stronger than anything happened in New Delhi attack on Israeli officials. Pakistan based terrorists had the temerity to plan a bomb attack on the Indian parliament itself a few years earlier.