"It was a heavy breakup for both of them because they were so excited about their future together," the insider continued. "The full-time transition to Nashville [for Holly] was their biggest hurdle and it just didn't work out in the end."
Luke and Holly had reconciled early this year after he "ghosted" on Stassi Yaramchuk following their appearance on The Bachelor Winter Games.
Luke and Stassi appeared to leave The Bachelor Winter Games as a strong and solid couple, having engaged in long conversations and bonded over their similar heart conditions.
However, during the show's reunion special in February, Stassi told host Chris Harrison she had never heard from Luke after The Bachelor Winter Games finished filming in December.
Luke told People that after The Bachelor Winter Games wrapped, he realized his heart really belonged to Holly the whole time -- an explanation he attempted to use to justify why he gave Stassi the cold shoulder when she confronted him about his behavior on the reunion special.
"During that time, I really started reflecting on where my heart was at and I started thinking a lot about my ex, honestly," Luke told People about Holly, who he had dated for a year but broke up prior to his appearance on The Bachelor Winter Games.
"I came to the epiphany of saying, 'My heart is with somebody else.' I wanted to make that clear, and that didn't take away from the fact that Stassi and I had that initial connection. She's amazing and she's great, and I want the best for her."
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During the February interview, Luke said giving his romance with Holly another chance was "the greatest decision I've made."
"We're together now and stronger than ever," he told People. "I'm in love with her. I'm just thankful that going on this show helped me to find where my heart really was and who my heart was with. I hate if Stassi was hurt in the middle of that."