You can check last edit in op, according to Sri Lankan's authority it was retaliation.
Edit 3
Sri Lanka says Easter bombing spree that killed 321 people was 'retaliation' for the mosque shootings in New Zealand
https://qr.ae/TWp4fVSeriously?
I don't think that we can justify one suicide attack by pointing out another one.
Also, in this case this theory doesn't make any sense. There is no indication that Brenton Tarrant, the perpetrator of the Christchurch terrorist attack was a religious Christian. He was a white nationalist who hated Muslims. And how can the Muslims retaliate by attacking a bunch of non-white Christians?
It doesn't have to make sense. It's Muslims....
Very few, if any, of their suicide bombing hysterics make sense to the typical Western mind.
Did 9/11 "make sense?"