My PDF export is lower resolution than high-quality viewing of InDesign document

[#1]

When I export my InDesign file as a high-quality-print PDF, my social-media vectors go from being high resolution to low resolution. 

For example, my FB vector  has an actual 72 ppi and an effective 8301 ppi. This is what it looks like in InDesign: 

Now, here it is when viewed in Acrobat Pro DC:

Also, when I printed the PDF, the vectors' resolution looked fine. I am baffled. 

[#2]

When I export my InDesign file as a high-quality-print PDF, my social-media vectors go from being high resolution to low resolution. 

For example, my FB vector  has an actual 72 ppi and an effective 8301 ppi. This is what it looks like in InDesign: 

Now, here it is when viewed in Acrobat Pro DC:

Also, when I printed the PDF, the vectors' resolution looked fine. I am baffled. 

[#3]

Vectors don’t have a resolution, so in your example the vector art has been converted to an image format—i.e. .png, .jpeg, .tif, .psd

The default High Quality PDF preset has its Compression tab set to downsample images with an Effective Resolution over 450ppi down to 300 ppi, so your 8301 ppi logo would be downsampled to 300ppi. You could increase the 300ppi downsample res, but it would be better to have a real vector version of the logo (.ai or .pdf) so that resolution isn’t an issue.