You are severely over estimating how much minecraft does, they have almost assuredly not even made the 2.5 billion back, they sold roughly 22 million copies in 2017 since in february of 2017 they reported 122 million copies sold, assuming the distribution of platforms remained constant since 2016 easily 40% of those sales are for the mobile version which is 7$ or roughly 62 million $, but ofc there is a very good chance that apple and google are taking 30% of that, so around 43 million (very rough calculations losing a few million here and there), then lets assume the consoles see around another 40%, which at 27$ is 240 million $, console sales have to pay their dues to the console manufacturer which is roughly another 30% depending on the method of distribution so lets say they get 167 million there, then you get around 20% pc sales for around 119 million $, here they get almost the full pie (there are payment processing fees, and they are sold through stores too but what ever lets assume 100% digital), so that is a total of 330 million in game sales, if we assume they made an equal amount in merchandise (which I have no idea where they are at) that would be 660 million $ in a year, then we know that from june 2016 to february 2017 the game sold around 15 million copies, so lets say that the revenue in 2016 was around 900 million $ with merchandising, and that in roughly half a year of 2015 they made another 660 million $, that would still leave microsoft around 300 million shy of making their money back, assuming they are making as much of the merchandising as they are on game sales, assuming 2016 was around 36% better than 2017, and that the time they had minecraft in 2015 was as good as the entire 2017, and that they had no costs, and that they paid no taxes on that revenue, and that they sold every single copy at full price.
So really Microsoft hasn't made their money back even doing things way above what they are likely to be in reality, now will they do their money back eventually? Sure. Was it a good purchase? Yeah.
But to do 2 to 3 times what it paid for it, minecraft would have to be pulling profit above any other game out there, and it isn't, stuff like league of legends far surpasses it, even some annual franchises, or ofc even non annual franchises like GTA which are also pulling insane amounts of money, the place where minecraft is truly king in games is not in revenue, but in mindshare among the younger demographic, it is an absolute beast there and the true reason why microsoft bought it in the first place.