I was mistaken, I found a copy of Jobs' letter re:Flash and he does cite the proprietary nature of Flash and Apple's lack of control over the content served on its platform as the most important reason Flash was kept off the iPhone.
> This becomes even worse if the third party is supplying a cross platform development tool. The third party may not adopt enhancements from one platform unless they are available on all of their supported platforms. Hence developers only have access to the lowest common denominator set of features. Again, we cannot accept an outcome where developers are blocked from using our innovations and enhancements because they are not available on our competitor's platforms
Funny how one could and maybe should point the same criticism towards electron.
Even in OS X it was still a bad plugin, one of Snow Leopard's headline features was that plugins were moved to separate processes so that Safari could keep running instead of bringing down the whole browser when a plugin had a problem.
If memory serves me right, that was one of the big raisons d'etre for Chrome (released in 2008)... so Snow Leopard (2009) was catching up with it more than solving a Mac specific issue. But yes, back then the big big plugin was Flash, and its security and performance left a lot to be desired (in all platforms).
https://www.cnet.com/culture/steve-jobs-letter-explaining-ap...
I used OSX and Flash in the late 2000s so I have no problem believing that.