The BBC itself, and multiple videos, are my source for the acclamation.

Goma, capital of North Kivu, already fell a few weeks ago., as it did previously on the 20th November 2012.

The word on the net is that we(sterners) aren’t using our dear sanctions against Rwanda, as we did in 2012, because we’ll gain even more money than through the current neo-colonialism, and i.d.k. if our theft/neo-colonialism will indeed be increased in case of a rwandan victory, it seems at most a partial explanation.
Apparently, the DRC had closer ties with Uganda recently, but i don’t think that Rwanda’s supposed “isolation” played any role.

There are manifestedly ethnic tensions, most notably the Tutsis genocide during the Rwandan Civil War in 1994. And, as usual, we(sterners) were biased when describing the context and saying who’s good and bad(, i’ve read the autobiography of Pierre Péan a few years ago who complained about our biases back then).
It does seem that the weight of past conflicts may be one of the main reasons :

The M23, mainly composed of congolese tutsis, is saying that the congolese government didn’t respect the 23 March 2009 peace deal, including the integration of CNDP’s members in the official army, and a protection of the Tutsi minority.
That includes a protection from the FDLR, whose continued existence and apparent support from the DRC may be an other valid reason for Rwanda’s attack.
They named their movement after this date, hence the 23 in M23 :

The DRC can’t do much to control their territory because like many rich african countries they’re too exploited to have a military strong enough to enable them to fully control their own territory, among other problems linked with neo-colonialism(, P.Lumumba was assassinated in 1961).

Another reason why Rwanda isn’t currently under attack by our medias is that Paul Kagame is apparently a respected leader who raised Rwanda’s influence in collaborating quite heavily with the United Nations peacekeeping missions, including against islamists in Africa(, most notably in northern Mozambique where France’s Total Energies is developing an offshore gas project) :

Also, « A decade ago, Rwanda’s primary exports were coffee and tea. Now it is a key supplier to the west of metals powering the tech and green energy revolutions, despite not having the mines capable of producing them. »
And the impact of western sanctions may be reduced because « In the years since, Kagame has built alliances with non-western partners such as China and the United Arab Emirates, which is now the country´s top trade partner. »

It seems like it’d be easy for the DRC to agree with the light&legitimate demands of the M23, i don’t see why they don’t, and risk instead a separatism in the worst case. Local opposition to their integration, structural problems in the army, ethnic tensions, distrust towards (ex-)rebels, …, aren’t valid enough reasons, so i.d.k.

That’s only a quick/incompetent overview.
What’s your opinion on this ?