Actually Popolocrois was also partially outsourced, but to the actual Popolocrois devs at Epics. It had both dev pedigrees behind it and still sold unimpressively.It's also somewhat important to note that PoPoLoCrois despite being a license(an SIEJ one at that) was both developed and published by the core SoS team. Doraemon is from neither so the "core" fanbase aren't necessarily going to buy in, at least straight away.
Doraemon is outsourced entirely (to a great dev admittedly in Brownies) and published/produced by Bandai Namco. All Marvelous has to do with it is apparently licensing the name, it's about as much a Marvelous SOS game as the 3DS spinoff was a Sony Popolocrois game.