Mostly it isn't that he likes well done steak with ketchup. Eat steak cooked any way you want! Also I think there's generally a US bias against putting any kind of sauce on a steak, which is stupid. A nice perfectly cooked steak without much on it is great, but there's nothing wrong with adding something to that, even ketchup if you like.
It's that if you're going to eat a hockey puck with Heinz, you don't need to pay $50 to do it. If you're paying $50 for a hockey puck with Heinz, you just think that if something costs more it must be better. That $8.99 steak and eggs at the local diner is probably going to be better. And, ok, fine, the Donald is super rich so who cares, but he actually isn't super rich, he's a grifter who lives an ostentatious life by floating from one line of credit to the next.
A $500 bottle of wine might be awesome, but if you can't tell the difference between that and two buck chuck, drink the two buck chuck. There's no shame in that.
I wrote "mostly," and there is one other issue, which is that for all of his supposed "riches," the Donald is a man who seems to have not gone beyond fancy steak houses and golf courses (and gold plated homes) in his appreciation for "the finer things." You can be an obscenely rich guy and love hockey pucks with Heinz, but if the breadth if your experience hasn't gotten beyond that more generally... that's sad!
The well done steak is a symbol.