Carlos Slim sold Tracfone to Verizon last year.
MVNOs buy network access wholesale from the three big network operators (AT&T, T-Mo, and Verizon), and some, like Tracfone, offered a choice of more than one network.
It doesn't make much sense for Verizon to keep buying something it can already provide itself, so it's moving all of those customers to its own network.
From a market standpoint, Verizon taking control of one of the largest prepaid service providers isn't going to benefit competition, as there will be one fewer independent player to keep them honest. They can both squeeze the low-margin MVNOs by lowering their prices just a bit and take their customers, start up direct competiton like Visible, or buy up the others, and play the long game to raise prices higher in the future, when they have even greater control.
As TV cord cutters have discovered, the content cartel are really the ones pulling the strings, so whether their stuff is being delivered by MSOs, OTT services, or in the new age of streaming, directly from in-house brands/services, they're going to get their blood from viewers regardless.