I think Hunter Biden was recruited to the BOD because his father was vice president, and the Ukrainians were hoping to get something out of it. Hoping to get something out of it, and actually getting something out of it, are two different things, and nobody alleges the latter. Hunter Biden was a troubled adult, who was exploited by the Ukrainians who, I imagine, felt even the appearance of a connection to Joe Biden was worth $50,000 a month, or whatever it was.
A lot of Presidents have had close relatives and friends who embarrassed them -- Jimmy Carter's brother, Ronald Reagan's gay son, Bill Clinton's wife and girlfriend ( 8-) ). No way to stop that.
None of that has anything to do with Trump's attempted extortion. You have to remember, it wasn't a request from Trump to look into Biden's son's employment that's the problem, it was Trump's effort at extortion that's the problem -- the withholding of U.S. government money from Ukraine, which had been authorized by Congress in an effort to help the Ukraine hold off Trump's buddy Vladimir Putin's troops, that caused the problem. I think if Trump had said, "Listen, pal, you should look into Hunter Biden's presence on the gas company board," there wouldn't have been an impeachable problem. The problem was when he said, "Listen pal, look into Biden or I'll withhold the defense money you need." Clearly extortion, and it wasn't his money to withhold.