Republicans are not much better, but Trump did win.
As I understand the DNC changed the nominating rules for 2020, and I am not up to speed on the changes. But in 2016 and before, they had a very large number of superdelegates and they gave proportional allocation of state delegates. Hypothetically a candidate could come in 3rd place with 20%-25% of the party voters in every state, and still come out on top either by gathering enough smoke-filled backroom superdelegates, or by the #1 and #2 vote getters changing frequently (e.g. more than 4 or 5 candidates some coming in 1st and 2nd in some states and 4th and 5th in other states) or some mixture of the two. It was basically rigged to give a lot of power to the insiders.
The GOP also had superdelegates, but not nearly as many, and the states were winner take all. No proportional allocation. Could you imagine how it would have shaken out if the GOP did give proportional delegates with 17 candidates vying for the win?