Why would the Russians have four tank programs?

If you lost sight of current Russian tank programs, Petri Mäkelä at Vantage Point North has you covered:

When these four parallel tank programs are looked at from a strategic perspective few alarming possibilities emerge. If the reason for the new modernization programs are either the delays in the T-14 Armata program on insufficient funds to purchase them in numbers, it hardly makes sense to divide the RnD and procurement funds to four separate programs.

Either the attrition from the increased training regime recently imposed to the Russian Ground Forces is proving to be too much for the older vehicles. The much more disturbing possibility is that Russia is planing to expand its military significantly or that it’s expecting massive attrition from an unspecified near future operation that have to be replaced rapidly.

On the other hand this could be the usual corruption ploy to waste government money to the completely unnecessary programs in order to allow the oligarchs and the officials to skim most of the budget in to their own pockets.

My guess is that it takes so long to produce the T-14 that they have to upgrade the older models too.