Thanks to OLN I've been following the Tour this year and noticed that the riders have some type of cover over their shoes. What is the purpose of the thing? It looks kinda like a cover a scuba diver would wear. Is it for aerodynamics, weather protection, or something else?

BTW they zoomed in on one riders rear wheel today and good lord thats a small cassette. I'm pleased if I can maintain 20 MPH I can't imagine maintaining 30+, and they all look like they have such scrawny legs too.

Yup!

Straight blocks (11-20. 11-21, 11-23) are fairly standard and look like corn cobs to the hoi polloi.. Remember most of the early stages are flat and lower gearing is not needed. Note the cadence, typically in the 80-100 range, and of course the speeds, which are in the high 20's, occasionally low 30'smph. Their small CW will be a 42t rather than 39t most doubles are equipped with, at least until the mountains when most go to 39t.
The torque these guys can generate is phenomenal. Few pros in the TdF, Giro, or TdS generate less than 0.5 hp average. Lance types are in the 0.75hp range. Steve