Several factors you need to consider:
1. I doubt if they had anticipated having to tear up the Ronaldo agreement right before the World Cup -- and needing to find a replacement in December. The cnut has to take the blame for this.
2. I suspect ETH has a very specific type of players he has in mind during transfer windows. Our scouting team is new and they are probably coming to terms with what ETH wants. So I am sure there are plenty of strikers in their database. But not many that suit what ETH is looking for in December that's available.
3. We are skint so there aren't many choices you can afford (at usually a premium) in January.
4. The Glazers are selling -- so anyone in their shoes will not be willing to splurge for an investment that you will not see any returns on.
So as far as planning, its all work in progress since ETH only got here at United some 6 months and a bit ago. And when you consider all those factors and have a Venn diagram we are left with very specific options -- we have to thread a needle to find the one that ETH wants and needs.