This has nothing to do with Ukraine or Russia, it has to do with the dynamics of American domestic politics,

He is right and wrong, it does have to do with Ukraine and Russia and the dynamics of American domestic politics. From a rather lengthy article on Zelensky that I found on the same page as your link:

So far it looks like Zelensky has been violating democratic norms to stay in power, though it’s unlikely it will help. Let’s look at the recent political history of Ukraine. Viktor Yushchenko, who pursued a similar policy, was elected in 2004 with 51.99% of votes and failed to get reelected in 2010, securing a miserable 5.45%. Poroshenko got 54.7% of votes in 2014 and only 24.45% in the next election. Zelensky’s approval rating now seems to be following the same pattern.

It appears Zelensky is about to go the way of Yushchenko and Poroshenko, the Biden administration doesn't want to see a Russian installed new president once and if Zelensky is voted out, to protect the Biden administrations political corruption similar to what was seen during the Obama/Biden administration and his son Hunters involvement.