It is the most weird thing ever. Theoretically this can not ever happen it is a breach of consensus. I've seen some people are suggesting it to have something with 51% attack, false!

An attacker with 100% hashpower can't enforce any consensu rule change including and most importantly block reward or to be more specific inflation policy. So what the heck?

I can imagine just one disappointing scenario: There are very few full nodes and the attacker has taken control of some while block explorers are using spv clients that have trust in compromised nodes. I'm still banging my head over and over to find other explanation.