The 54-year-old stopped coaching Murray in March, having helped the Brit win the 2012 US Open and 2013 Wimbledon for his maiden grand slam titles.
Neither party elaborated on the decision behind the split, with Lendl saying he wanted to focus on his "own projects".
But, speaking to British media on Sunday, Lendl said family commitments and his inability to give Murray the time needed were behind his decision.
"It was lots of little things combined. Like playing more on the vets tour, and one of my daughters returned home," Lendl said.
"The youngest one is 16 and she had been away at horse-riding school and but now she has come back to live with us.
"My mum is now 79 and lives in Prague, I need to go more to the Czech Republic than I used to.
"The planes are a pain in the arse. The places, the hotels - England was good, Australia was good, here it was all right. It was the smaller trips I didn't like.
"All these things combined. And you know with Andy, after his [back] surgery and after winning Wimbledon and all that, I felt that if anything he needed more time rather than less time."
Murray has teamed up with Frenchwoman Amelie Mauresmo and begins his US Open with a clash against Dutchman Robin Haase on Monday.
Lendl said he would be open to a return to coaching, when the time was right.
"Maybe eventually if the situation is right. But the time now is not right. It wouldn't have worked if Andy had called me two years earlier, or if he had called me two years later," he said.
"And it has to be someone I feel I can offer something to. If it was John Isner for example I am not going to be able to tell him how to hit a serve."