There seems to be some misunderstanding about tenaim, I’ll try to explain it a bit.
In Europe, especially 18th and 19th century,but also before and after, many shidduchim were made without the man and woman having met. Life was tough, between pogroms, limitations on travel, death from disease and many other factors, it was not possible to “hang out in a hotel lounge and see what comes of the match”. There was alot of trust put into whoever suggested the match, and often large sums of money. The Chassam Sofer was often asked to arbiter the percentage of the dowry that the Rav receives for performing the marriage. The community also recieved a percentage from one or both parties. The terms of the marriage were negotiated and quibbled over, often as if it were a high-end business deal.
If one of the parties pulled out, there was major embarrasment and often serious financial loss. It was not to be taken lightly. There were penalties that were spelled out in the contract for whomever backed out and they were stringently enforced. These penalties were not only financial , but spiritual in the way of curses and ominous consequences for the future. Sometimes these penalties were so overwhelming and the conditions so stringent that it was decided to go ahead with the wedding anyway. This is why sometimes it was said that a divorce is better than breaking the tenaim. It also explains a shtar mechila for the party that was harmed.
Nowadays, these severe conditions are rare . Agreements are made, but not necessarily in stone. The tenaim is often a formality at the wedding that simply states that the conditions were met and everybody is ok with it. It is done for traditional purposes and not for contractual purposes.
There are probably still circles, mostly chassiddish, who take their tenaim very seriously and maybe even append penalties to them. In that case, yes, it can be a serious matter to break them. Since all these minhagim are community and rabbinically administered, each one goes by their own rov and posek and lives with the decision.