Well, the Modi-led Indian establishment brought out this scheme for two reasons :
1. Modi's PM candidature manifesto for 2014 had one of the promises being to provide two crore jobs ( 20 million )
every year if he was voted as PM. Eight years have passed and he is into his second prime minister term ( the second election was in 2019 ) and no two crore jobs every year in sight. In fact there is huge unemployment. Now there is another prime minister election in 2024, just two years away so Modi wants to either become PM again or put forward the Hindutvadi Dilon Ki Dhadkan, Yogi ji, currently chief minister of Uttar Pradesh. Either way Modi wants a BJP person to be PM for eternity or until India doesn't become a Hindu Rashtra. But to get votes for the next from-BJP PM he should make good on his promise to provide jobs, that too to the demographic that is most present in the country and that demographic generally falls in the category who the establishment decided to take into the Agnipath scheme. So this scheme is one part a votes gathering program. Some more on that in
this article.
2. The second reason is partly what
@lastofthepatriots alludes to in post# 2. BJP and the rest of the Hindutvadis want a large cadre of military-trained youth who end up genociding the three main enemies of Hindutvad - Muslims, Christians and Communists - and suppress others like revolting Sikh farmers and then the anyways oppressed Shudras and Dalits. All this will be in the glorious cause of Hindu Rashtra. Now such a large required set of militias will be drawn from two sources : (a). Hindutvad-aligned youth who you can find on the internet. In fact an opposition party leader from the South Indian state of Karnataka
has already spoken of such an intention of the BJP government, (b). Non-Hindtuvadi youth who can be sufficiently brainwashed to contribute towards genocide and then establishment of Hindu Rashtra by using words like "They are anti-national", "They are the Tukde Tukde gang", "Those people believe in ideologies foreign to our land of Sanatan Dharma ( Hindutvadi name for their beliefs meaning "A system of supreme traditions that never had a beginning and never has an end" )... words like these.
Please read above.
@Skull and Bones