Well its up to 2/3 of the forces he had at the border are now committed within Ukraine. And he has had to ask for help from Belarus. One thing that has been noted is the poor equipment, with vehicles being abandoned. However yesterday I saw a video of Russian MREs that had been captured, they had a use by date of 2015. And today I saw video of some Russian POWs in WWII helmets. This leads to 2 options:
1) He has sent in his shit soldiers and equipment first, to sacrifice it and wear down Ukrainian forces.
2) All of his equipment and soldiers are of equal shitness.
If it is 1, then he could not have expected a quick win in Ukraine if he was sending in sacrificial troops first. If he did expect a quick win then 2 is the most likely option.
However this raises the question about his air force, they have not been involved and would surely have made a huge difference to their objectives. So again there are a few main reasons:
1) They are not as good as they should be (some reports of pilots having around 100 hours annual flight time, vs RAF and US Air Force where they pilots complain that less than 200 flight hours per year is not enough to remain combat ready).
2) He needs the for stage 2 of the plan which would mean fighting NATO when he tries to invade Poland or other neigbouring Baltic state (There is no way he can get his forces from Ukraine to Finland without Finland having lots of notice and preparing... posssibly by joining NATO anyway)
3) It might be “Better to remain silent and be thought a fool than to speak out and remove all doubt.” If his air force flew and we saw they were in as much dissaray as his land troops there goes any concern over Russian air superiority.