Theres a rumour going around that Michael only agreed to do 10 shows, he went to bed one night selling 10 shows and woke up the next day and sold 50, its complete BS if u ask me, for starters the timing doesnt add up bcoz the extra shows were added over a period of about 24-36 hours, MJ must have been in bed for a long time. And also u couldnt pull off organising an extra 40 shows within a few hours, Michael knew about those extra dates.
Im sure he wanted to do it for a few reasons and seeing how happy he looked in "this is it" makes me certain he wasnt forced to do it.