To understand why some miracles have seemingly differing results, you need to put the miracles into a context. And there are two. Two broad groups - those Miracles he did in the early part of his ministry, and those later. But more, you need to see the ‘difference’, the ‘why’.
Those in the early part of his ministry were ‘signs’. That is, they were ‘foretold’ in the Tanakh (Old Testament). These were ‘signs’ that the Messiah would perform - and only the Messiah would be able to do these. These were specifically to announce the arrival of their Messiah. Example, healing someone born blind.
Because they were prophesied, they ‘would be’, that is, they would ‘happen’ independent of the recipients ‘faith’ - because prophesies ‘will be’. Gods word, what God has spoken, will come to pass.
But after being ‘rejected’ as Messiah, Jesus went about ‘doing good’. He already had a reputation of being able to deliver, but those seeking a miracle now required ‘faith’, the persons ‘faith’.
So now there is a ‘variable’ - or, in other words, the miracle was dependant on something outside of Jesus. So we see ‘your faith has made you well’, or, ‘as you have believed, so be it done unto you. Note ‘your faith’, ‘you’.
So, we see, for example, when Jesus could not ‘do’ any (great) Miracles, (Mark6:5) , if people’s ‘faith’ was lacking, (unbelief), he would ‘build’ it up by straight away starting to teach them.
As well, he would sometimes have to move away from people casting or generating unbelief - go out of the town, or tell everybody to leave the room.
So .... The blind man who was only ‘partially healed’, needed his faith ‘built up’. (a little more).
The point here is it is people’s faith, not Jesus’s ‘power’, that was the variable. And, we appreciate this now comes into a contentious ‘zone’, so will leave it here. Nevertheless, it is an answer to this question.