Love motivates people to work through challenges that might otherwise lead them to give up. If those founders had focused on building for a customer they genuinely loved, they would have been more likely to persevere and create something that addressed a deep need. If they were to find a customer they loved serving, I would invest in them again.
I was at Amzn early '00s when we lost 95% of our market cap. Later at FB I negotiated a down-round in '09, and then in '12 our stock dropped 50% post-IPO. I was on the board of a public company that went bankrupt (Borders) and a start-up that went under (Hello). Some lessons: