Reason(s) are improper account creation and / or niche and / or improper campaign setup.
There is no way anyone could clearly and correctly alert you about the exact of these reasons, in your case unless one also has a look at your campaign. Why ? Let us assume it is due to campaign, in that case LOTS of aspects in the campaign could be the reasons : a FEW OT THE LOTS of campaign reasons are high daily budget, incase of search campaign even a single improper keyword or even a single improper word nowadays leads to account suspensions & when I say improper, I mean improper as per Google Ads review algorithms. I repeat : These are ONLY A FEW OF THE MANY MANY MANY improper campaign triggered suspensions.
And note that even if it is an improper campaign triggered suspension even then in many cases suspension reason would show as due to suspicious payment.
Regarding proper account creation, I mean proper as per the overall algorithms of Google Ads and nowadays methods to create Google Ads accounts is a premium thing and that is why no one will openly and freely and fully share their working methods. If such a method is shared freely openly & fully, it means it is an already saturated method and no longer working.
At the most some kind members may share some useful hints & tips, for example "use residential IPs", "change browser & device fingerprints", "try a different card", etc, etc.
Various people have various account creation methods : For example, some people do not use residential IPs, but still have good success in creating threshold Google Ads accounts. So, there would be sometimes conflicting experiences, as what works for one person may not work for another person, as various people may implement the same thing in various different ways. Also search in this AdWords section itself regarding this issue, as the exact same has been discussed in more than a dozen long threads and you would get a wider insight and as I have shared my thoughts & suggestions, I'm sure other members would also share theirs, which could be useful for you.
In some cases I have seen members realizing finally that they have to in reality hire a Google Ads expert and they post in "Hire A Freelancer".