I don't understand your argument at all.
Turkey had two chances to take Austria, but didn't, and that means he's obviouly a multi/meta gamer? It looks to me like Turkey just won the game (without stabbing Austria), so why would you assume that he needed/wanted/should-have/had-to have stabbed Austria?
Your argument only could've made sense (to me, perhaps I'm missing something..) if:
*Austria* (the weaker of the two allied countries) had multiple (and superb) opportunities to stab Turkey (the stronger ally) but declined to do so.
That would imply that Austria (the weaker of the two countries) was voluntarily passing up a chance for a guaranteed win in order to allow another player (Turkey) to win.
Such behavior would be surprising, but even then, it's hardly proof of anything. In reviewing some of my opponents games I've observed several examples of closely allied countries dominating the board and growing together, and then (instead of taking a draw as you might expect), one of the countries allowed the other to win, even supporting/convoying the other into one of their centers.
Such behavior is a little surprising, but in a PPSC (points per supply center) game, first place and 'second' place are not nearly as important as the number of SCs you finish with. (assuming you're playing for points). In such games, it may often make sense to support a stronger player in the hope of gaining SCs while the other player wins. The alternative (to challenge the stronger player) makes it much more likely that you'll get squashed by the strong player (along with the other weak players who will probably stab you for their own meager gains) and thus finish with few/no SCs at all.