All due respect, "pretty good" is a bit of an understatement. He was, statistically speaking, the best QB in football over their last 8 games, leading the youngest team in football to a 6-2 record, leading the league in TDs over that period, 18:1 TD/INT ratio, and completion percentage, etc. In the playoffs, he led said young team to a total dismantling of the Cowboys, on the road in Dallas, in the Wild Card round. He finished #2 in the league in TDs, second only to Dak. They had seen enough. They did the same exact thing with Rodgers in 2009 when they were just 4-3 and he was putting up middle of the road numbers.
You don't do what Love did (literally every impact WR and TE are still on rookie contracts) by chance. It's so hard to identify franchise QBs in the NFL, and it's arguably the most important success factor in all of sports, identifying your guy under center. They paid him for his potential, which he has loads of. They're only going to grow based on how young they are.
I don't criticize the Packers at all for extending him so early; I do criticize them for waiting all offseason though, as it cost them more millions after seeing the Trevor Lawrence and Tua contracts get finalized, as well as valuable practice time last week as he was holding out of the physical portions of camp.