This all boils down to major corruption by the DNC and the Obama Administation...something the Democrats nor the maistream media don't want to touch with a 10 foot poll. Too many heads will roll and they know it. Obama stacked the top brass in the intelligence (and other)agencies with partisan hacks. (see Brenner, Strzok, Clapper, etc.)This was a way to both shield his administration from wrongdoing and to do exactly what is being done to Trump. Obama weaponized these groups to his and his party's benefit.
With regards to this call with Ukraine, Trump said "do me a favor" investiage corruption, specifically mentioning CrowdStrike and the DNC server. He later mentioned Biden, who was certainly part of a very fishy situation with his son while he was Vice President and was tasked to reduce corruptiion in Ukraine. That being said, the "favor" was not a direct reference to the Bidens. He probably shouldn't have done so and given the Democrats ammunition, but the phone call was with the Ukraine and they were discussing corruption involving the Ukraine and the US. The DNC server and the Biden situation both involve potential corruption which directly invole the US government or government officials. He said "do me a favor", he didn't say, "I am not going to give you the aid if you don't do xyz". If there was an actual quid pro quo, don't you think there would have been some parameters placed around it? What qualifies as an investigation? Ukraine would probably have liked to know what specifically they would need to do to prove they were investigating before receiving the money. None of that occurred, because where was no quid pro quo.