I just finished the entire series. Although there is some mixed reviews for the ending. Here is my take. Please skip if you haven't watched the show contains spoilers.
I think people are missing the main reason which led to hyun woo getting reincarnated as Do jun. It was cause his loyalty towards the company was misused and he was basically used and thrown as garbage in the sea. He was a common man whose life was practically not worth a penny as he was born poor.
Cut to Do jun who was the charismatic lovable witty heir born with the silver spoon still murdered by his own family because of jealousy and greed for the throne.
If Do Jun had lived as chairman the actual revenge of hyun woo would still be not complete as his actualy family is still living in poverty and conveys the message that the common man is still suffering
As Hyung woo has already lived the life of the heir he himself was able to realise although from a rich conglomerate every single one of them are still people with so much insecurities, ignorance, lack of empathy who don't deserve to head such a big company.
It gave him the confidence to fight the giant leaders such as Soonyang who had the likes of Ministers and Politicians and avenge the death of the rightful heir (Do Jun) and attempted murder of himself.
The past can never be undone so Do jun's death was inevitable. But bringing down the entire company for his death just by a confession passed on the message that the common man with no actual power won just cause of his honesty which is a much better message than the conglomerate heir's victory cause of gaining power.
PS : Do Jun fan 💔