It used to be when you did a search in the market Place and then selected one of the items that a new tab was opened for that item. I remember someone complaining about that functionality and maybe it was changed because of that, but it should be changed back ASAP.
The way it works now is very annoying and time-consuming, because the item is opened in the same tab, which would be OK, but when you use the Back button, you don't get the previous page with the search results, but some unrelated page. As a result, you need to do the search again, remember at which page you were at, continue searching, select an item, which will open in the same tab, and then rinse and repeat. The only way to circumvent this is of course by right-clicking and selecting the option to open the item in a NEW tab, which was the original functionality that has been removed.
I tried both Chrome and Edge, and they both have this undesirable behavior, so it's not a browser problem.
If for seem reason opening a new tab is problematic (I wouldn't know why), then at least ensure that the search results are still there when using the Back button.