Fed had BP's 2 different games in the 3rd set too, people tend to forget that and only focus on the 0-40 game he got out of at 3-3.
As for 4-1 you've watched and played the game enough to know that no good player loses 5 straight games on grass unless they are screwing up royally. His serve abandoned him and he was hitting tons of errors. Also you have to remember what was going on recently, he got blown out at RG and earlier that year he blew a 5-1 lead at Hamburg and lost the first set, and he blew a 4-1 lead (I think) in both sets of Monte Carlo. Those collapses were playing a factor and a big part of why he came out innpathetic fashion the first couple of sets.
Also 2008 clearly wasn't the height of his powers, that'd be 2006. 2008 was like Rafa's 2014, mostly chalked full of disappointing results.