They are investing a lot of money in their Lego TV shows out of blind faith.
Now that's completely incorrect.
The TV market model is different to the game market model. TV Stations and Networks buy the rights to show the program on their station; the station then receives profit via advertisers. Each station knows what the best and worst time-slots are, and so the best shows go to the best-time slots and also receive the highest-paying advertisers, which makes everybody happy in the end.
LEGO is consistently getting their shows in the top rated slots for the children networks, which in turn means a stable amount of profit. Even if you discount the fact the TV shows are giant commercials for their LEGO toy lines and help sell those, when you add on additional profit from DVD distribution and other unrelated merch sales, LEGO is making a killing on some low budget 3D animation.
It was blind faith when LEGO attempted a TV show that involved live CGI way back in the 90s, but since then their work with companies like Tt (who do a lot of their animation as well as their games) is really starting to pay off.