Since SST is relatively stable (compared to more volatile things like air temperature) and is generally increasing, it’s actually not unprecedented for it to be setting new daily record highs for an extended period of time. That happened during the 2016 el niño as well. It’s just that this time it went on for longer than ever (I think) and was breaking previous records by an amount that’s quite large for most of that time.

It’s now no higher than it was last year, but it still has a long way to go before it reaches temperatures observed in years before that.