The 29-year-old left for relegated West Ham in a £4million move last month after failing to win the long-term contract he was looking for, much to the horror of Magpies fans who saw their team's inspirational captain contribute 12 goals to the cause last season.
Pardew was disappointed to lose Nolan, who had two years remaining on his existing deal, but insisted there would have been little point in keeping a disgruntled player.
He told BBC Radio Newcastle: "Kevin didn't want to stay, that's the end of the debate. Kevin couldn't get a contract for four or five years.
"My opinion is that we couldn't give Kevin a five-year contract because if Kevin isn't playing first-team football, he isn't going to be the leader that we want, I am convinced of that.
"Kevin is so full-on as the captain of a football club and at the level he has gone to now, he will easily cope with that and he will come back to the Premier League.
"But in four or five years' time, Kevin needs to be doing the business in the first team, and we couldn't and I couldn't see that possibly happening here at Newcastle, and we had to make a decision on that."
Pardew also has a decision to make with his goalkeepers with veteran Steve Harper, Holland international Tim Krul and Fraser Forster, who enjoyed a successful spell on loan at Celtic last season, all vying for the number one spot.
Indeed, one of the three is likely to be playing his football elsewhere during the next campaign rather than operating as number three at St James' Park.
Asked if he would keep all three, the manager said: "Probably not, actually, and that's a situation we have to be very careful of.
"They have all got a genuine, genuine chance to be number one, so when you suddenly become number three, that's a major issue and that will be a major issue for one of them.
"That's something we will have to deal with. In my mind - and hand on heart, I can say this - I haven't really got focused on one particularly goalie.
"Harps was great for me [last season]. He is brilliant in the changing room, he is brilliant in and around it, he knows Newcastle inside-out, he knows how it ticks.
"He will be important to us this year and he wants the number one shirt; Tim wants it - he has just had a brilliant game against Brazil in a full international; and Fraser is coming off a great season.
"It's a great situation for me, but I do need to make a call and I will genuinely, genuinely take all into account - Harps' history, Harps' experience against Tim's inexperience, but natural God-given talent, as with Fraser."