What happened was terrifying, so it's understandable that people try to make sense of it. I think the speculation did go totally over the top though, and some people did get perverse pleasure out of having something to bash Muslims and/or migrants with.
But it's very nieve to claim that no one should have even thought of a link to religion or race. Acts of this sort are, in Western Europe, generally carried out by Muslim extremists, usually of migrant background.
I have Irish heritage, and when a bomb went off in London in the 70s and 80s, I know that the first thought of most people would have been the IRA, or simply 'the Irish'.
As a society we all have to work on integration, on supporting levelling up, on countering extremism and preventing ghettoisation.
I hoped the attack wasn't by a Muslim extreamist, as I know from family members who lived in the UK in the 70s and 80s that they were blamed by some for all IRA atrocities, and I don't want all Muslims in the UK to face the same pressure.
But to be shocked that anyone would wonder if the attacker acted in the name of Islam is disingenuous and virtue signalling.