Is the reduced shelf space more an indication of the rise of online shopping or a decline in sales? I'd imagine it's a mixture of the two, but I'm sure theres' not a 1:1 relationship between reduced pegs and reduced sales.
It's also inventory management. If one peg holds 8 figures like Nick was saying, that one peg is now holding $120 in TVC inventory. Back in the 5POA days when TLJ/TFA/Solo figures were $8 each, that same inventory $ amount would have been 15 figures on two pegs. It just feels like Target isn't willing to sink $ into holding too much inventory at one time anymore.
The cost of making these figures is everything. The cost is affecting the make-up of the line (character selection, need for re-use, 50% of figures being repack/repaint, etc). It is affecting how much stock retailers are willing to hold. It is forcing some collectors out (reduced sales). It is forcing others to rethink their habits (buying online vs daily toy runs), which in turn hurts brick and mortar retail sales and their inventory and the cycle continues.
I still love collecting this line (3.75" Star Wars), but man I wish TVC was dead. I wish they would have killed the bubble which would have forced them to rethink the 3.75" line. They could have come up with cheaper, smaller, easier to ship packaging (like the trooper 4-pack boxes). They could have pivoted to putting some 5-10POA weirdo figures into the line occasionally to help offset the cost of the SA figures without people bitching "this isn't up to TVC standards". Mainline figure costs wouldn't have had to jump to $16.99 this spring.
Alas, collectors bitched, the bubble stayed, and here we are with our $17 "look how we fixed/updated/repainted the figure this time!". The card and bubble sure look cool though!

(I know easy for me, an opener to say - I get that the look/style of the bubble/cardback is everything to some buyers... but that ain't me.)