Ahead of the Azerbaijan Grand Prix, AlphaTauri revealed that Tost would be stepping down at the end of this season, with his Italian outfit to be run by Ferrari sporting director Mekies and new CEO Peter Bayer.
But the announcement of Mekies' recruitment did not go down well at Ferrari, as it was unaware of the development. Its team principal Fred Vasseur said the timing of the press release was "a bit aggressive".
ANALYSIS: Why Vasseur thinks Mekies exit won't harm Ferrari
Speaking in Baku on Saturday morning, Tost said that AlphaTauri's hands were forced into making the announcement when it did because the news had already started leaking out – with Italian newspaper Gazzetta dello Sport reporting it on Tuesday.
"The announcement, to tell you the truth, was not planned to come up now," he explained. "This was planned much later.
"But as you all [journalists are] very professional, there were some leaks in the press. And I didn't want to come here to Baku - it was in the Gazzetta dello Sport, for example, that Laurent will come to us - and to tell all to you, 'No, I don't know anything,' because it's not the way of how we are working.
"So, we said 'OK, we go out with the press release.' It was planned to do at a later time in the year. But now it's out. And of course, I can imagine that some people are not happy about this."
Tost said he has been thinking for a while about his long-term future in the sport and had communicated long ago to senior executives at Red Bull, including the late Dietrich Mateschitz, that he wanted to step down before he was 70.
"It was my decision," he explained. "It started already two years ago; I discussed it also with Dietrich Mateschitz in those days.
"I'm now 67 years old and, when I was younger, I always said to myself, if you're in a leading position, then you should not glue on the seat, you should give this position to younger people, more clever people, creative people, motivated people. And now I'm going to the 70s, it's time to say goodbye.
"I love Formula 1. I like all of you as well. But it's a story which once has to end. And especially now with the solution, with Peter Bayer as CEO and with Laurent Mekies, we have two fantastic people who will replace me. And I think it's the best time to go out from Formula 1."
