There are a few reasons for it:

• In countries at peace handing over these kinds of armaments comes under public scrutiny - and public announcements from one country shift public mood in others.

• Russia would probably notice at least some of the tanks being moved anyway - they require a lot of logistical support.

• Since Russia can't be invaded for the war to end unfavourably either their morale or ability to fight needs to be crushed. Announcing a shitload of weapons hurts the former, the weapons themselves hurt the latter.

There's also not all that much Russia can do that they wouldn't attempt anyway. For instance, if they were capable of an offensive to pre-empt these deliveries they'd probably launch one anyway even without knowledge of them.

Also, Ukraine and the West have been quite good at misleading the Russians so far this war - for example they were led to believe that a Kherson offensive was imminent, and then were hit with an entirely different offensive at Kharkiv. So there is a good chance a vital piece of the story hasn't been made public.

Wagner are essentially a parallel army that's outside the normal command structure - the Kadyrovites are the same. Putin is still at the top, but the rest of the hierarchy is absent (which in theory makes them more flexible and makes it easier to learn what is really happening).

Back in World War II this was sort of done with the NKVD though their units were put in the Red Army when it was necessary (most famously at Stalingrad). Germany's SS was likewise an army outside the usual Wehrmacht command structure - gaining more power throughout the war as Hitler distrusted his generals.

The reason they are in fierce competition is because they're trying to win the same resources from the centre. The army has struggled to get these resources because its leaders aren't part of the ruling clique (who are instead drawn from the "siloviki" - high ranking FSB and other security services).

It would need to have ~100 millibar partial pressure of oxygen to be breathable - with at least an extra 20 millibars of inert gases (or more oxygen).

Without biology oxygen doesn't stick around, so as with the early Earth the atmosphere was probably a mix of carbon dioxide and methane.

To nitpick; Earth is about 70% the distance Mars is - it gets roughly twice as much sunlight rather than four times as much. Venus in turn gets about twice as much as Earth and four times as much as Mars.