First of all, Vegas picks winners. Not a team that’s actually competing, they pick themselves.
Next, the so-called point spread moves to take advantage of money flow. Occasionally, an injury could effect the betting margin, but most times it changes where the suckers put their bets.
And, plain and simple: sports books, point spreads, U/O, etc., are based entirely on getting suckers to part with their money. Gambling “gaming” and it’s influence is a growing cancer which can only lead to the collapse of sports.