My question is that why to keep somebody waiting for 9 months for such rejection.
You are mixing up two issues here, the rejection "without proper review" and the delay, and I think that's illogical and they need to be addressed separately. So first of all, it's not actually clear to me that it's fair or necessarily correct of you to say the paper was rejected "without proper review". There was a review -- two of them in fact -- you just don't like that one of the reviewers didn't think the paper was up to the standards of the journal. This is a perfectly valid and legitimate reason to reject a paper (one I have used myself on various occasions), and while the report could be a bit more detailed about why the reviewer doesn't think the contribution is important, it's quite possible that this is an entirely subjective matter and there's really nothing useful they could add in terms of justification. So in what sense exactly was the review "not proper"? Moreover, you seem to cite the facts that reviewer 1 liked the paper and that the paper was later accepted to a good journal as evidence that reviewer 2 was being wrong or unreasonable, but I see nothing of the sort; it is perfectly acceptable and reasonable (and common) for reviewers to hold different opinions. After all, if they always agreed, prestigious journals wouldn't have a need or desire to send a paper out to two separate reviewers, would they?
The second issue concerns the 9 month delay to get a decision. Again, I think this should be addressed entirely separately from the outcome of the review. It is in fact reasonable in my opinion to complain about such a long delay (and would be reasonable even in the case of an acceptance), but the conclusion you take away here is again incorrect. You ask:
Is the message that "Unless you are completely sure that it is a path-breaking work don't send to SIAM, otherwise it will be time waste".
Well, no, in my opinion the message is rather "if you really care that much about your paper getting accepted (or rejected) fast, don't send it to the most prestigious journals, which are precisely the ones that have to handle the largest number of submissions from all the other authors competing to publish in them." Keep in mind that the editors of those journals are very successful and (as a result) very busy mathematicians, their workload is high, and the referees they approach to review papers are also very successful and hence very busy mathematicians, who despite their own heavy workload are nonetheless occasionally shamed into agreeing to increase their workload further by accepting thankless and uncompensated refereeing assignments, in many cases out of a sense of guilt or because they are bad at saying no (a very common problem among academics btw). Is it a surprise that some of them might drag their feet in completing their assignment? No, it really isn't.
The bottom line is that if you can't afford to wait 9 months for a decision on your paper, you are free to send your paper to a predatory journal that will reach a decision (that is sure to be positive, another advantage) in a few days, or to a legitimate but less competitive journal that might do an honest job in more than a few days but in less time than 9 months. Yes, it sucks that the academic publishing system in math sometimes (not always) works this way and we haven't been able to reach a point where authors always get detailed reviews and in a reasonable amount of time. But that's life, and that's the best system currently available, and it's precisely the most prestigious journals that suffer from it most (statistically speaking at least; I'm sure there are exceptions). The best that you and your friend can do to change this is to be the change you wish to see in this world, and make sure that when you get requests to review a paper, that you deliver a great report and do it in a reasonable amount of time.