Realistically speaking, the sort of size expansion of a star to super giant preceeding the supernova we see in the game usually takes place over billions of years and doesn't happen in a matter of minutes, so it's an anomaly that the sun is expanding at such a rapid rate.

Though Outer Wilds isn't exactly realistic, I'm not sure that the logic follows. There's an exhibit in the museum that explains the death cycle of the start for a reason, I think. I don't think it's intented to be due to an impact from The Interloper even within the Outer Wilds universe.

Furthermore Chert himself is surprised by the rapid expansion of the sun. He also notes that all stars in the universe are exploding at an unusual rate. By the end of a time loop, you notice that the sky is almost entirely devoid of stars.

The universe is just dying.