Reasons for Google Ads suspending accounts, is when the Google Ads overall algorithms and the Google Ads review algorithms detect any violations of the Google Ads policies. However, apart from Google Ads policies, nowadays, in fairly new Google Ads (threshold & non-threshold)) accounts, suspension can also happen due to things which the Google Ads algorithms detect as "suspicious", for example, drastically increasing daily budget and a lot more apart from this. So, even if a whitehat campaign went live, but the user performed some campaign related operation(s) which the Google Ads algorithms detect as "suspicious", account would get suspended, with suspension reason showing as suspended due to suspicious payment, yes, you read it right, with suspension reason showing as suspended due to suspicious payment, though in reality it is not anything to do with payment, billing, card, etc.
I do realize that few (actually in reality many) people are unable to think out of the box and will ask "How can Google Ads algorithms detect a drastic increase in daily budget, as "suspicious" ???" ... Ask and I will mention how.
Sometimes, nowadays, merely just changing the payment method can get account suspended. Yes, there are many legit Google Ads partner agencies running whitehat in their legit agency Google Ads accounts (old accounts with huge spending history) and their accounts have got suspended just because they did some minor normal thing such as changing the payment method and upon appeal, Google Ads replies that the suspension is final and also upon further contacts and explanantions to Google Ads, still Google Ads says the suspension is final.
The above is the reality of how Google Ads is as of today and hence Google Ads itself is nowadays encouraging people to rather go for churn and burn Google Ads threshold accounts.
And, in 99% cases of Google Ads showing suspension reason as due to suspicious payment, in reality it has absolutely nothing to do with payment, billing, card, etc.
Nowadays, if one creates a new GAds account and the GAds algorithms "see" that as an account created for churn & burn purposes, then the account will get suspended. However, one reality is that those who know how to create and how to use churn & burn threshold GAds accounts, are still doing so without issues (80% to 90% accounts going live).
I request to be pardoned for mentioning the reality of how Google Ads is nowadays. But, those who accept reality, will then know how to proceed next, by trying things in a different way. Those who deny reality will continue to do things the same way and will continue to get accounts suspended.
Once again, I request to be pardoned for mentioning the reality. It may give some useful direction to a few people and the rest may just simply ignore the reality I've mentioned and perhaps just simply continue your old ways of using Google Ads, which as per numerous threads in the Adwords section, no longer works, many people are nowadays getting only accounts suspended. In life overall, sometimes accepting the reality, results in progress, because when we accept reality, then we start to do things in a different way, start experimenting and then finding the way out would be possible.