Normally you cannot put particles straight after verbs, but in old Japanese this was acceptable and common. There are still remnants of this usage, and you’ll often see things like
<verb>がよい which is a common (stiff) expression similar to
<verb>たほうがいい (sounds very rough/imperative).
However, another common one is using past tense + はいい + が/けど, just like in this example sentence:
There is a good explanation on Japanese stack exchange about it.