Нет бы выбрать блиц-раунд, они выбрали вопрос с подвохом.

Нет бы + infinitive is a common colloquial pattern that expresses reproach, regret, or irritation about a better action that did not happen.

So here, Нет бы выбрать блиц-раунд... means something like:

• They should have chosen the blitz round
• Why couldn’t they have chosen the blitz round?
• Instead of that, they could have chosen the blitz round

It is not a literal use of нет meaning simple negation. The whole expression works as one idiomatic unit.

Because this construction normally uses the infinitive to name the action that would have been better.

Pattern:

• Нет бы + infinitive

Examples:

• Нет бы подождать — They should have waited / Why not wait?
• Нет бы спросить — They should have asked

So Нет бы выбрать блиц-раунд means Choosing the blitz round would have been the better idea, but that is not what happened.

The two parts do different jobs:

• выбрать names the preferred but unrealized action
• выбрали states the actual action that really happened

So the sentence has this logic:

• Better option: choose the blitz round
• What they actually did: they chose the trick question

That contrast is exactly what gives the sentence its tone.

The subject is understood from the second clause: они.

Russian often leaves out a subject when it is easy to recover from context. Here, the listener naturally understands:

• Нет бы [им] выбрать блиц-раунд...

In fact, Russian can make that explicit with the dative pronoun:

• Нет бы им выбрать блиц-раунд...

That version is also natural. The original simply omits it because они is immediately supplied in the next clause.

With infinitives, Russian often uses the dative to mark the person who is supposed to perform the action.

So:

• им выбрать = for them to choose / they to choose

This is a normal Russian pattern with infinitives. Compare:

• Мне идти? — Should I go?
• Тебе решать — It is for you to decide
• Им бы подождать — They should wait

So if the subject is stated with нет бы + infinitive, it is often in the dative.

Because the sentence refers to a single completed act of choosing.

• выбрать / выбрали = to choose / chose, as a completed result
• выбирать / выбирали would suggest an ongoing process, repeated choosing, or focus on the activity rather than the result

Here the point is that they made one specific choice, and it turned out to be the wrong one. That is why perfective is the natural choice.

Both nouns are direct objects, so they are in the accusative case. But for masculine inanimate singular nouns, the accusative looks exactly like the nominative.

So:

• блиц-раунд → accusative блиц-раунд
• вопрос → accusative вопрос

That is why there is no visible ending change.

A contrast:

• выбрать стол — choose a table
• but выбрать брата — choose a brother

Here брата changes because брат is animate.

Because the preposition с in the meaning with normally takes the instrumental.

So:

• с подвохом = with a catch / with a trick in it

The noun is:

• nominative: подвох
• instrumental: подвохом

This phrase is very common in Russian:

• вопрос с подвохом — a trick question, a question with a catch

Russian often leaves the contrast unstated when it is obvious from context. The comma here joins two clauses in a sharp, conversational way:

• Нет бы выбрать блиц-раунд, они выбрали вопрос с подвохом.

The meaning is effectively:

• They should have chosen the blitz round, but instead they chose a trick question.

Russian could add a conjunction, for example а, but the version without it sounds more compact, emotional, and colloquial.

No. Нет бы + infinitive is colloquial and expressive. It sounds like spoken Russian or informal narration with attitude.

A more neutral way to express a similar idea would be:

• Вместо того чтобы выбрать блиц-раунд, они выбрали вопрос с подвохом.
• Им следовало выбрать блиц-раунд, но они выбрали вопрос с подвохом.

Those versions are more neutral.
Нет бы adds a feeling of Come on, that would have been the obvious thing to do.

Not exactly. Вместо того чтобы is the straightforward neutral way to say instead of.

Нет бы includes an extra emotional layer:

• criticism
• annoyance
• hindsight
• sense that the better choice was obvious

So in many contexts, instead of is part of the translation, but нет бы is stronger than a simple neutral comparison.

Putting Нет бы выбрать блиц-раунд first sets up the speaker’s complaint before stating what actually happened. That order makes the contrast stronger.

First comes:

• the better option they failed to take

Then:

• the bad option they actually chose

That is why the sentence feels expressive and slightly dramatic. Russian word order is flexible, but this version gives the sentence its natural punch.