Leverkusen wanted to sell Havertz, needed the money more than Dortmund does and Havertz had more of a reason to leave due to there being no CL football. That's why it was 'easier' to negotiate that deal. It's not that difficult to understand. It's a lot harder to negotiate with a team that has no intention on negotiating because they are more than happy to keep said player.
In regards to Sancho - the consistent briefs makes me think this is just posturing from us, to eventually blame Sancho and his reps for why the deal didn't go through, them being greedy etc. It's probably the only way that they believe they can save face by pulling out of this.
If they say it's due to Dortmund's valuation, we come off looking like we aren't as financially stable etc. as we seem, not good for PR, shareholders etc. and goes against the notion that Ed keeps pushing that we are some juggernaut with infinite reserves. Alternatively though, if we blame the demands of himself and his agent, we make it seem like we are taking a stand to overpaying players and their greed is the reason they didn't end up joining. I see no other reason why they would keep leaking this info, it does nothing for anyone. Risks alienating the player/pissing him off and just frustrates the fans.