That's not so much done for diversification but geography and economics.
Poland has regions where -just like in Ukraine- the average Western tank is at times to heavy to operate properly. The K2 is more than 10 tons lighter and Poland scrapped several original requirements to keep it that light because that's the whole point. Also the K2PL variant additionally comes with (partly) modular composite armor.
And Poland wants domestic production (and the neccessary tech transfer to facilitate it). Something that South Korea is allowing for better footing in the wider European market.
That doesn't make the decision for US Abrams as the main tank better.
Aber es waren nunmal Linke und da haben die üblichen Verdächtigen jede Menge Gründe das erstmal ungeprüft in die Welt zu posauen. Man muss schließlich das wahre linksgrüne Feindbild aufrecht erhalten, sonst könnte der deutsche Michel versehentlich selber denken und feststellen, wie er verarscht wird.