Kompakte Pflanze, warum?

Like GrowCN explains, it is better to have bushy plants. All bud sites receiving equal amount of light, leads to a bigger and much more quality harvest. Some plants will just grow compact naturally, with short internodes and uniform canopy. This is mostly a matter of genetic that determine shape and levels of natural hormones the plants produce. Some factors may contribute to excessive stretching, like your environment: poor light level, high temps, overcrowded tent. And there is a few tricks to contain stretching, like pruning and training your plant, topping it, using a SCROG, high level of light, wind stress... But a Thai sativa will never show the structure of an indica. Some growers are just letting the plants do their thing like nature would. Some others will do extra work to keep plants low and even.

I think a lot has to do with the lighting. When I switched to my current lights my plants are shorter, bushier and produce more. Are you saying you want your plant to stretch more airy??? I think your plant is looking good. I expect you are going to get some stretching now but not all varieties stretch the same amount.