(SPOILERS EXTENDED) Tyrion's advice to YG

I think Tyrion telling Aegon to march west is actually a very smart move, and it benefits him significantly.

Tyrion thinks it's a stupid idea, but it's actually the best piece of advice possible to give.

Firstly, the situation in Westeros is tenuous at best. The Lannisters are a spent force, the North and Riverlands are wastelands, the Stormlands are eagerly waiting an opportunity to strike, and Dorne, the Tyrells and the Vale sit with basically full strength armies, the first 2 houses amenable to a Targ restoration.

The leaders in Westeros are awful, as Tyrion mentions, and if Aegon met up with Dany, he would have to spend years mopping up Meereen's mess for Dany with his large force. By then, winter would have come, and Westeros would be impossible to retake. Yeah, they could strike in the spring, but by then, Westeros would have recovered and would be able to handle a Targaryen invasion.

Striking west, with the advantage of surprise, works wonders as Aegon wipes out the remaining Lannisters, and once word comes to Dany that her nephew, her potential marriage alliance, is fighting a war as a rebel to restore Fire and Blood, she is much more likely to come to his aid.