The centre-back, who left for Wolves last month, feels Ashley has shown his ambition after Newcastle were the highest spending team in the Barclays Premier League during the transfer window.
The Magpies spent around £29million on Jonjo Shelvey, Henri Saivet and Andros Townsend, as well as loaning Roma forward Seydou Doumbia.
They also failed in a £21million move for West Brom's Saido Berahino as they try to beat the drop.
Nevertheless, it took Ashley's spending this season to around £83million and Williamson insisted he cannot be criticised for his efforts.
He said: "They can't knock him for the money they spent in the summer and this transfer window.
"He came out and stated he wanted to win something and wouldn't leave until they did, he has got ambition.
"The fans will judge it on the consistency and how they progress from here."
Williamson also backed the Magpies, who lost 3-0 at Everton on Wednesday, to survive with the club two points from safety.
He said: "Steve McClaren is a good guy, I learnt a lot from him. He creates an optimistic environment and they deserve to be higher.
"I hope the players they've brought in have added a boost and they can turn it into points. They will be fine, they have more than enough."
Williamson left St James' Park for Sky Bet Championship Wolves after six years and 170 appearances, scoring twice, for the Magpies.
He had struggled to break into McClaren's team this season, playing just twice in the League Cup. The 32-year-old returned to Molineux after a five-game loan spell last year and admitted leaving the north-east was tough.
"It was emotional," said the ex-Watford man. "I've had a lot of highs and I feel honoured to have made the amount of appearances I did.
"Promotion from the Championship, playing in Europe, beating Sunderland 5-1, Manchester United 3-0 and we beat Arsenal at the Emirates. I thank fans for the support they've given me."